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MODERN PRACTICE 


OF THE 

ELECTRIC TELEGRAPH. 

A HANDBOOK 


ELECTRICIANS AND OPERATORS. 


y 

y 


WITHDRAWN u#. 

Tr. to IiC 

NOV 2 2 1916 


By FRANK! i L; POPE. 

I.IPMIA0V, " j 

Tv* eyas*' oio 


TENTH EDITION. 

REVISED AND ENLARGED. 


pew Doth: 

D. VAN NOSTRAND, Pullisher, 

23 Mubbay Street & 27 Wabren Street. 







/ 



By Tr«33»f«r 

APR 1917 


Rntered according to act of Congress, In the year 1872, by 
D. VAN NOSTRAND, 

la the Office of the Librarian of Congress, at Washington. 



t l 
ft ‘ 


A < 






PREFACE TO THE FOURTH EDITION. 


During the quarter of a century which has elapsed since the 
introduction of the Electric Telegraph in the United States, those 
engaged in its service have been almost entirely dependent upon 
verbal instruction, and long practical experience, for a thorough 
technical knowledge of their profession. The works accessible 
to the American telegrapher have been of a popular, rather than 
of a strictly scientific character, or else of so elementary a nature 
as to be of little service except to the most inexperienced stu¬ 
dents. It is true that a number of excellent foreign works have 
appeared within a few years ; yet the difficulty and expense of 
obtaining them, as well as their want of applicability to the 
American telegraphic system, has prevented their general circu¬ 
lation among the class for which this work is more especially 
designed. 

The unexpectedly favorable reception which has been accorded 
to the first three editions of this work, lias led the author to 
believe that it has, to some extent, supplied the acknowledged 
deficiency which had previously existed in this branch of litera¬ 
ture. The present edition has been carefully revised, as well as 
enlarged by the addition of much new matter, and is believed to 
embrace all the recent discoveries and improvements in practical 
telegraphy, which have successfully passed through the test of 
actual experience. 

The methods of testing telegraph lines and apparatus by actual 
measurement, which are now universally employed in Europe, 
and to some extent in this country, have been treated upon to 
an extent commensurate with the importance of the subject. It 
is hoped that, with the aid of this work, the student may obtain 
a complete and satisfactory knowledge of this useful and beauti¬ 
ful system. 

The principles laid down for the guidance of the student in 
the formation of the telegraphic alphabet, and the subsequent 




IV 


PREFACE. 


progressive exercises intended for practice with the key, differ 
but slightly from those employed by the author, while teaching 
a class of students for the American Telegraph Company in 1864. 
This plan was believed at that time to be original, but as a method 
of teaching, involving substantially the same principles, was 
devised and subsequently published by Prof. J. E. Smith, in his 
Manual of Telegraphy, it seems proper to make this explanation 
of the circumstances. 

Among the additional matter in the present edition will be 
found an entire new chapter upon the Recent Improvements in 
Telegraphic Practice, as well as a number of articles in the 
Appendix, on the Equipment of Telegraph Lines, the Working 
Capacity of Telegraph Lines, and the Electrical Tension of Bat¬ 
teries and Lines, etc., etc. 

Most of the illustrations in this volume have been engraved 
expressly for its pages, from original drawings by the author. 

In conclusion, the author desires to express his acknowledg¬ 
ments to his friend David Brooks, for much valuable aid in the 
preparation of this work, especially of the present edition ; and 
he would likewise take occasion to thank M. G. Farmer, for 
information which has been kindly supplied by him. Much 
useful material has also been obtained from Sabine’s Electric 
Telegraph, Gulley’s Hand-Book of the Electric Telegraph, Clark’s 
Electrical Measurement, Yarley’s Report on the Condition of the 
Western Union Lines, and the columns of The Telegrapher. 

Elizabeth, N. J., January, 1871. 



1 







CONTENTS. 


CHAPTER' I 

ORIGIN OF THE ELECTRIC CURRENT.—GALVANIC BATTERIES. 

PA«F. 


Simple Galvanic Circuit. 9 

Conductors and Non-Conductors. 10 

Electrical Tension. 11 

Electrical Quantity. 11 

The Daniell Battery. 12 

Effect of Continued Action. 13 

The Deposit of Copper upon the Porous Cup. 14 

Renewal of the Battery. 14 

Application of the Daniell Battery to Main Circuits. 15 

The Grove Battery. 15 

Setting up a Grove Battery. 16 

The Carbon Battery. 17 

Power of the Carbon Battery. 19 

Insulation of Batteries. 20 


CHAPTER II. 

ELECTRO-MAGNETISM. 


Deflection of the Magnetic Needle. 21 

Electro-Magnets. 22 

Intensity and Quantity Magnet. 22. 


CHAPTER III. 

TELEGRAPHIC CIRCUITS. 


Resistance of the Circuit. 24 

Electrical Measurement. 25 

Resistance Coils. 25 

Simple Telegraphic Circuit. 25 

The Earth Circuit. 26 

Arrangement of the Batteries. 26 

Intermediate Stations. 26 







































VI 


CONTEXTS 


TAGE. 

The Morse System. 2G 

Other Telegraphic Systems. 27 

CHAPTER IV. 

TIIE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 

The Morse Signal Key. 28 

Tho Morse Register..... 29 

The Relay Magnet. 30 

The Sounder. 32 

Arrangement of a Terminal Station. 34 

Arrangement of a Way Station. 35 

Adjustment of the Apparatus. 36 

Switches or Commutators. 37 

The Plug Switch. 39 

Tho Universal Switch. 39 

Arrangement of tho Connections. 41 

Jones’ Lock Switch. 41 

Lightning Arresters. 42 

Tho Plate Arrester. 43 

Bradley’s Arrester. 43 

Repeaters. 45 

Wood's Button Repeater. 46 

Hicks’ Automatic Repeater. 47 

Milliken’s Repeater.. 50 

Bunnell’s Repeater. 52 

Combination Locals. 55 

Local Circuit Changer. 56 

Technical Terms used in the Telegraph Service. 57 

CHAPTER V. 

INSULATION. 

Tho Glass Insulator. 59 

The Wade Insulator. 60 

The Hard Rubber Insulator. 60 

The Lefierts Insulator. 61 

The Brooks Insulator. 61 

Brooks' Stone-ware Insulator. 62 

Mode of Testing Insulators. 62 

Escape. 63 

Weather Cross. 63 

Effect of Escapes and Grounds upon tho Circuit. 63 

Tho Laws of the Electric Current. 64 

Practical Application of Ohm’s Law. 65 







































CONTENTS. yj[ 

PAGE. 


Distribution of Battery Power... 70 

Working Several Lines from One Battery. 71 


CHAPTER Y I. 

TESTING TELEGRAPH LINES. 


Interruptions to which Telegraph Lines are Liable. 13 

Testing for Disconnection. 74. 

Partial Disconnection. 75 

To Test for an Escape. 75 

Testing foi» Grounds. 76 

Testing for Crosses. 76 

Testing with the Galvanometer and Resistance Coils. 18 

Testing for the Distance of Faults. 80 

The Loop Test. 81 

Blavier’s Formula for Locating an Escape. 84 

To Find the Distance of a Cross. 85 

Advantages of Testing by Measurement. 86 

Testing for Conductivity Resistance. 87 


CHAPTER YII. 

NOTES ON TELEGRAPHIC CONSTRUCTION. 


Poles. 89 

Wire. 89 

Galvanized Wire. 90 

Arrangement of Wires upon the Pole. 90 

Joints or Splices. 90 

Fixing tho Insulators. 91 

Leading Wires into Offices. 92 

Fitting up Offices. 93 

Ground Connections. 93 

Cables. 93 

Making Joints in Cables. 94 


CHAPTER Till. 

HINTS TO LEARNERS. 


Formation of the Morse Alphabet. 96 

Elementary Principles of the Alphabet. 97 

Exercises for Practice in Sending. 99 

The Alphabet and Numerals. 101 

Reading by Sound... 102 

































CONTENTS. 


• • • 

Vlll 

CHAPTER IX. 

BECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 

The American Compound Wire. 104 

The Gravity Battery. 106 

Siemens’ Universal Galvanometer... 108 

Pope and Edison’s Printing Telegraph. 112 

CHAPTER X. 

APPENDIX AND NOTES. 

The Equipment of Telegraph Lines. 116 

The Working Capacity of Telegraph Lines. 121 

The Electrical Tension of Telegraph Batteries and Lines. 124 

Double Transmission. 131 

Edison’s Button Repeater. 134 

Bradley’s Tangent Galvanometer. 135 

Thompson’s Reflecting Galvanometer. 137 

Mode of Working the Atlantic Cable. 141 

Velocity of Electric Signals. 144 

Speed of Transmission. 145 

Comparison of Wire Gauges.* *. 146 

Useful Formula for Weight and Resistance of Wires. 147 

Conducting Powers of Materials. 147 

Internal Resistance of Batteries. 149 

Electro-motive Force of Different Batteries. 150 

Measurement of Electro-motive Force. 151 

Forces of Electro-magnets. 151 

Electrical Formulae. 152 

Ohm’s Law. 152 

Parallel or Derived Circuits. 153 

Galvanometers and Shunts. 153 

Formula for the Loop Test. 153 

Blavier’s Formula for Locating a Fault. 154 

Measures of Resistance. 154 

Strain of Suspended Wires. 154 

Index. 157 

































MODERN PRACTICE 

or TUB 

ELECTRIC TELEGRAPH. 

CHAPTER I. 

ORIGIN OP THE ELECTRIC CURRENT.-GALVANIC BATTERIES. 


1. Simple Galvanic Circuit.— If two plates of dif¬ 
ferent metals, such as copper and zinc for example, are 
immersed in a vessel of water to which a small portion 
of sulphuric acid has been added, and the upper ends of 
the two plates are brought in contact, or connected 
together with a metallic wire as in fig. 1, a continuous 



Fig. 1. 


current of electricity will pass from the copper to the 
zinc through the connecting wire, and from the zinc to 
the copper through the liquid, as indicated by the 
arrows in the figure. If the metallic communication be 
interrupted, or the circuit , as it is termed, broken, the 
current at once ceases, but is instantly renewed when¬ 
ever the connection is again formed. Electricity pro¬ 
duced by this means is usually termed Galvanic or Vol¬ 
taic electricity, from the names of its discoverers, and 
is the effect of chemical action by the acidulated water 
upon the zinc. 












10 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


2. The plate (usually of zinc), upon the surface of 
which the electricity is generated by chemical action, is 
called the negative pole, and the opposite plate, gen¬ 
erally of copper, platina or carbon, is called the posi¬ 
tive pole. They are also frequently designated by the 
signs —(minus) and + (plus). 

3. If both metals in this arrangement were equally 
acted upon by the solution, no electricity would be pro¬ 
duced, as this effect arises in all cases from the differ¬ 
ence in the chemical action upon the two plates. For 
this reason the positive plate is made of some metal or 
other substance upon which the liquid has little or no 
effect. 

4. The apparatus for producing voltaic electricity, 
which has been described in its simplest form, is called 
a battery. As electricity is produced under any circum¬ 
stances in which the above conditions have been com¬ 
plied with, there are various methods of constructing 
a battery. The forms used in the practical operation 
of the telegraph will hereafter be described in detail. 

5. Conductors and Non-Conductors. —Some sub¬ 
stances, such as metals, possess the property of allow¬ 
ing electricity to diffuse itself freely throughout their 
whole substance, and are therefore termed conductors. 
Others, such as glass, hard rubber, and dry wood, offer 
great resistance or opposition to this diffusion, and are 
called non-conductors or insulators. 

6. This division however is relative and not abso¬ 
lute. Few if any bodies are perfect insulators, and 
even metals, the most perfect of all conductors, offer 
some resistance to the passage of electricity, or in other 
words insulate slightly. A good insulator, therefore, 
is simply a bad conductor, and vice versa. 

7. In the following list each substance named con¬ 
ducts better than that which precedes it, the first being 
the best insulator and the last the best conductor : 

1. Dry Air, 5. India Rubber, 9. Silk, 

2. Paraffiue, G. Gutta Percha, 10. Dry Paper, 

3. Hard Rubber, 7. Sulphur, 11 . Porcelain, 

4. Shellac, 8. Glass, 12. Dry Wood, 



GALVANIC BATTERIES. 


11 


13. Dry Ice, 

,14. Water, 

15. Saline Solutions, 

16. Acids, 

17. Charcoal or Coke, 


18. Mercury, 

19. Lead, 

20. Tin, 

21. Iron, 

22. Platinum, 


23. Zinc, 

24. Gold, 

25. Copper, 

26. Silver. 


8. Electrical Tension. —If two or more simple bat¬ 
teries, or elements as they are called, are connected to¬ 
gether in such a manner that the positive plate of the 
lirst is united by a metallic conductor with the negative 
plate of the second, and so on, as shown in fig. 2, the 



Fig. 2. 


electrical tension , or power of overcoming resistance, is 
increased in direct proportion to the number of ele¬ 
ments. Four elements will therefore possess four times 
. the tension of one element, and the current generated 
by their combined action will be capable of overcoming 
four times the resistance of that from a single element. 

9. Electrical Quantity. —It is important, however, 
to observe, that although the tension increases with 
each element added to the series, no greater quantity is 
produced by a great number of elements than by a 
single one—the action in each cell serving only, as it 
were, to urge forward a quantity equal to that arising 
from chemical decomposition in the first cell. If, on the 
contrary, we connect together the four zincs and the 
four coppers, forming in effect a single clement, with 
plates 'equivalent to four times the original surface, 
there will be four times the original quantity of electri¬ 
city generated ; but its tension, or power , of overcom¬ 
ing resistance, will be no greater than that of a single 
pair of plates. This distinction is of great importance, 






















































































































12 


MODERN PRACTICE OF TITE ELECTRIC TELEGRAPH. 


and should be thoroughly understood and carefully re¬ 
membered. 

10. In the simple form of battery previously described 
(8), if the poles are united by a conductor for a consider¬ 
able length of time, bubbles of hydrogen, arising from 
the decomposition of the water, cover the positive plate, 
and in a great measure prevent the liquid from coming 
in contact with it, and the surface of the plate also be¬ 
comes coated with a deposit of zinc, tending to convert 
the battery into one in which both plates are of zinc, 
and thus its electro-motive force is weakened and finally 
destroyed. In order to render the battery constant in 
its action, it is necessary to prevent these effects by 
surrounding the negative plate with a solution of a salt 
of the metal itself. This principle is employed in the 
arrangement about to be described. 



Fio. 3. 


11. The Daxiell Battery. —This combination con¬ 
sists of a jar of glass or earthenware, F (fig. 3), about six 










































































































































































































































































































GALVANIC BATTERIES. 


13 


inches in diameter and eight or nine inches high. A 
plate of copper, Gr, is bent into a cylindrical form, so as 
to fit within it, and is provided with a perforated cham¬ 
ber, to contain a supply of sulphate of copper in crys¬ 
tals, and a strap of the same metal with a clamp tor 
connecting it to the zinc of the next element. H is a 
porous cup, as it is technically termed, made of unglazed 
earthenware, six or seven inches high and two inches in 
diameter, within which is placed the zinc, X. This is 
usually of the shape shown in the figure, which is called 
the “star zinc,” but it is often made in the form of a 
hollow cylinder, the latter giving greater power, but 
being somewhat more difficult to clean. 

The-outer cell#is filled with a saturated solution of 
sulphate of copper (blue vitriol), and the porous cell 
with a solution of sulphate of zinc. A series of three 
elements connected together, as usually employed on 
American lines for a local battery , is shown at I. 

12. Effect of Continued Action. —By continued 
action sulphate of zinc is formed in the porous cup, and 
the sulphate of copper in the outer cell consumed, the zinc 
being constantly dissolved away while the copper plate 
is at the same time increased. When all tlie sulphate 
of copper has been decomposed, and the water in the 
zinc compartment saturated with sulphate of zinc, the 
action of the battery ceases. Some of the sulphate of 
zinc in this case usually passes into the copper cell, and 
appears upon the copper plate in the form of a black 
powder ; it is therefore necessary to maintain a con¬ 
stant supply of pulverized vitriol in the perforated 
chamber attached to the copper cylinder. 

13. When the solution in the porous cup becomes satu¬ 
rated with sulphate of zinc it crystallizes upon the zinc 
plate, interfering with the action of the battery. Part 
of this solution should therefore be removed occasion¬ 
ally and replaced with water. 

In setting up the battery pure water may be used in 
the porous cell, and the battery allowed to stand a few 
hours with a closed circuit, when it will be fouo*i 



14 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


ready for use. The addition of a little sulphate of zinc 
will greatly hasten its action. 

14. The Deposit of Copper upon the Porous Cup.— 
This cannot be entirely prevented, but may be greatly 
lessened by suspending the zinc so that it will not touch 
the porous cup below the surface of the liquid, and by 
saturating the bottom of the cell to the height of half 
an inch with melted paraffine, or even tallow. 

15. When constructed as above described and used 
in a local circuit, the Daniell battery will continue in 
action about ten or fifteen days without attention, the 
time depending upon the size of the wire in the magnet 
and the amount of daily service. The sulphate of cop¬ 
per solution should be kept of good strength, otherwise 
the upper portion becomes weak and an extra current, 
is set up within the battery, which tends to eat away 
and destroy the copper plate without any useful effect. 

16. Renewal of the Battery. —In renewing this 
battery the zincs should be scraped and well cleaned 
with a stiff brush, the porous cups thoroughly washed, 
and the old solution, contained in them thrown out, with 
the exception of about one third of the clear portion, 
which should be returned, otherwise the battery will 
require some hours to recover its full strength. The 
copper deposit upon the zincs is valuable, and should be 
preserved. 

Every two or three months the coppers ought to be 
taken out and the deposit upon their surface removed, 
which may be done two or three times. When they 
become too much encrusted to afford room for the po¬ 
rous cups they must be replaced by new ones. 

Porous cups ought to be renewed whenever they be¬ 
come too much encrusted with copper. If cracked they 
should be changed at once, otherwise a great waste of 
material will ensue. 

17. The crystals which form around the edge of the 
outer jar require to be occasionally wiped off with a 
damp cloth, or they will eventually run down the out¬ 
side and form a connection between the jars, giving rise 



GALVANIC BATTERIES. 


15 


to a great consumption of material without correspond¬ 
ing benefit. 

18. In order that the current may act with its full 
force, it is necessary to keep the clamps and connec¬ 
tions of the battery clean and bright, and free from rust 
or dirt. As chemical action is promoted by heat, the 
battery will act more vigorously if kept in a warm 
place. 

19. Application of the Daniell Battery to Main 
Circuits. —This battery is sometimes used for main 
circuits, but in that case it is preferable to arrange it 
differently by placing the zincs outside and the copper 
within the porous cell, as in fig. 4, in which Z shows the 



Fig. 4. 


zinc and P the porous cell. The copper, C, is provided 
with a perforated shelf, D, upon which the vitriol is 
placed. 

Other forms have been devised which dispense en¬ 
tirely with the porous cup, the two solutions being sepa¬ 
rated by the difference in their respective specific grav¬ 
ities. Some of these bid fair to come into extensive 
use. 

20. The Grove Battery. —The most intense and 
powerful voltaic combination that has yet been dis¬ 
covered is that of Grove. For many years it was ex¬ 
clusively used for telegraphic purposes in this country, 
and is still employed in that capacity to a considerable 
extent. Its component parts are shown in fig. 5, in 
which A represents a glass jar or tumbler, about 3 













































inches in diameter and 4 2 inches high. A thick cylin¬ 
der of zinc, B, of a size nearly sufficient to fill the turn- 
bier, is placed within it, and is furnished with a project¬ 
ing arm, to which is attached the positive plate of the 
next element. The porous cup, C, is placed within the 
zinc. A thin strip of platina, D, about 2h inches long 
and half an inch in width, is soldered to the end of the 
zinc arm projecting from the adjacent cell, and reaches 
nearly to the bottom of the porous cup. 

21. Setting up a Grove Battery. —It is necessary 
that the zinc should first be thoroughly amalgamated. 
The ordinary zinc of commerce contains particles of lead, 
iron, and other impurities, which, when the plate is im¬ 
mersed in dilute acid, form as it were small batteries 
upon the surface, which eat away numerous cavities in 
the zinc without producing any useful effect. This is 
termed local action , and may be, in a great measure, 
prevented by the above process of amalgamation, which 
is usually performed by immersing the zincs in a vessel 
containing dilute muriatic or sulphuric acid, and then 
plunging them in a bath of metallic mercury. After 
remaining in this for a minute or two they are taken 


l 






























































































































































































































GALVANIC BATTERIES. 


17 


out and placed in a vat of clean water, where the su¬ 
perfluous mercury is allowed to drain off. The mercury 
dissolves a little of the zinc, which flows over and covers 
the impurities, and prevents the acid solution from 
coming in contact with them. 

22. In putting the Grove battery together, first place 
the glass tumblers in position and fill them about half 
full of a solution composed of one part of sulphuric acid 
and twenty to thirty parts water, by measure, thoroughly 
mixed. Then place the amalgamated zincs in the 
tumblers, with the arms turned at right angles to the 
line of cells. Fill the porous cups nearly full of strong 
nitric acid and place them within the zincs, then turn 
the zincs around so as to immerse the platina strips in 
the nitric acid of the adjoining cell, throughout the 
whole series, as shown at T, in tig. 5. 

23. The strength of the dilute sulphuric acid solu¬ 
tion in this battery should be varied in proportion to 
the number of wires worked from it. The less the num¬ 
ber of the latter the weaker the solution may be made. 

24. When in continuous service a Grove battery 
ought to be taken apart every night, and the nitric acid 
from the porous cups emptied into a vessel and kept 
closed until morning. The zincs should be removed 
and placed inverted in a trough of water, acidulated 
with sulphuric acid, and in the morning rubbed with a 
brush, and the mercury diffused evenly over their sur¬ 
faces. To every ten parts of the nitric acid taken from 
the battery add one part of fresh acid every morning. 
By this means a steady and uniform current will be 
maintained when the battery is in action. The dilute 
sulphuric acid requires renewal about twice a week. In 
handling this battery great care is required not to injure 
the connection between the zinc and the platina. A set 
of Grove zincs, in continuous service, will require re¬ 
newal about once in three months. 

25. The Carron Battery. —This is a modification of 
the Grove battery, and is sometimes called the Electro- 
poion battery. It is extensively employed on the Ame- 

2 



18 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


rican lines for main circuits. In its general construction 
and arrangement it differs but little from the battery 
last described. The different parts of which it is com¬ 
posed are shown in fig. 6, consisting of a glass tum¬ 
bler, zinc and porous cup. In place of the platina of 
the Grove battery, a plate of carbon or coke is em¬ 
ployed for the positive element, as shown in the figure. 



Fig. 6. 


A clamp is arranged so as to press a platina button 
firmly against the carbon, this button being permanently 
attached to a wire leading to a binding screw on the 
zinc arm of the next element. The parts are usually 
made of about the same size as in the Grove battery. 

The carbon connection is sometimes made by means 
f a platinized copper wire inserted into its upper end, 
;and surrounded with lead, to prevent the action of the 
vacids upon the copper. 

26. In setting up this battery the different parts 










































































































































































































































GALVANIC BATTERIES. 


19 


should be put together in the position they are to oc¬ 
cupy, as shown in fig. 6, and care taken that all the con¬ 
nections are firmly screwed up. The zincs must be 
thoroughly amalgamated, and the dilute sulphuric acid 
solution mixed as directed for the Grove battery. A 
sufficient quantity of this solution is poured into the 
tumblers to cover the cylindrical portion of the zincs. 
The porous cups are then filled with a solution of bi¬ 
chromate of potash,* care being taken not to pour it 
upon the connections or clamps. 

27. When the battery is in service, one third of the 
bi-cliromate solution in the porous cups should be re¬ 
moved every morning by means of a large rubber sy¬ 
ringe, and replaced with fresh. A new set of zincs will 
require to be amalgamated a second time after having 
been in use three or four days ; after which once in two 
to four weeks will be often enough—depending some¬ 
what upon the amount of work required from the bat¬ 
tery. The battery ought to be taken apart every two 
weeks, the zincs brushed, the dilute sulphuric acid solu¬ 
tion renewed, and the carbons thoroughly soaked in 
clean water. It is better, if possible, to have a spare 
set of cells complete, so that one may be renewed while 
the other is in use. 

28. Power of the Carbon Battery. —This is quite 
equal to that of the Grove, as far as the intensity of its 
action is concerned. The latter however will work 
nearly twice as many wires at the same time as the 
former. The expense of the carbon battery for mate¬ 
rials and attendance is less than one third that of the 
Grove. A set of zincs, if properly cared for, will last 
from fourteen to sixteen months on an ordinary tele¬ 
graph line. It is a good plan to coat the zincs with as- 
phaltum varnish at the junction of the projecting arm, 
as these are frequently eaten off while the rest of the 
zinc remains in good condition. 

* This solution is made as follows: Mix one gallon of sulphuric acid and three 
gallons of water. Then, in a separate vessel, dis-olve five lbs. bi-chromate of pot¬ 
ash in two gallons of boiling water and add to the above, mixing the whole thor¬ 
oughly together. The proportion of bi-chromate is sometimes made one fifth greater 
than the amount given. 




20 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


29. Insulation op Batteries. —The cells of a bat¬ 
tery should always be thoroughly insulated from each 
other. This is especially important in the case of the 

Grove battery. A convenient and 
effective mode of insulation is shown 
in fig. 7, in which the battery tum¬ 
blers, AA, are set upon hollow cy¬ 
linders of wood, BB, saturated with 
asphaltum or paraffine, and insulated 
from the upright wooden pins, DD, by 
the glass sockets, CC. The pins are 
inserted into a horizontal scantling, 
E, which forms the top of the battery stand. 

Battery jars, of different sizes, are now made at the 
Brooks Paraffine Insulator Works, in Philadelphia, which 
are composed of stone-ware, thoroughly saturated with 
paraffine, so that moisture will not penetrate them, nor 
remain upon their surface. When these jars are em¬ 
ployed, no special insulation is required. 












































CHAPTER II. 


E LECTRO - M AG X ETIS M. 

30. Whenever the poles of a battery are connected 
by a conductor, or series of conductors, so as to form a 
circuit, a current of electricity is assumed to flow from 
the negative to the positive pole, through the battery 
itself, and from the positive to the negative pole through 
the conductor. 

31. If the conducting wire is covered with an insu¬ 
lator (5), such as silk or cotton, so as to compel the 
current to traverse its entire length, and is wound into a 
spiral or coil, surrounding a magnetic needle, the needle 
will be deflected from its natural position, and will tend 
to take up a position at right angles to the direction of 
the current. If the current be passed in the opposite 
direction through the wire, the deflection of the needle 
will also take place in the opposite direction. The Gal¬ 
vanometer, an extremely useful instrument for the pur¬ 
pose of indicating the presence, direction, and strength 
of a voltaic current, is constructed upon this principle. 

32. If the conducting wire, covered as above, be 
wound upon a bar of soft iron, the iron becomes mag¬ 
netic as long as the current continues to flow, and pos¬ 
sesses the property of attracting other pieces of iron in 
its vicinity. This arrangement is called an electro¬ 
magnet. (34.) 

33. If the iron is very soft and pure it loses its mag¬ 
netism instantly upon the cessation of the current, but 
if impure, or if hardened by hammering or turning, it 
retains, a certain amount of residuary magnetism , espe¬ 
cially after it has been acted upon by a powerful cur¬ 
rent. It is, therefore, necessary that the iron cores, as 
they are termed, of electro-magnets, should be annealed 
with great care. 



22 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


34. Electro-Magnets are generally made in a U 
form, two bobbins or spools, a a (fig. 8), being filled 

with covered copper wire, and the 
soft iron cores, c c , passing through 
them, fixed upon a connecting bar, 
b , also of soft iron, as shown in the 
figure. The two spools, a and a, are 
virtually continuations of one spool, 
the direction being apparently re- 
Fig - s. versed by the bend of the U- The 

ends of the cores, c c, opposite to the connecting bar, 
are called the poles of the magnet, the magnetic force 
being accumulated at these points. The bar of soft 
iron, d, upon which the magnet exerts its force, is called 
the armature. 

35. In electro-magnets and galvanometers the mag¬ 
netic effect of the current is multiplied by the number 
of convolutions of the wire in the coil, but it is dimin¬ 
ished in proportion to the distance of the wire from the 
core, each layer of wire acting with less power than the 
one beneath it. 

36. Every addition to the length of the conducting 
wire enfeebles the current, because of the increased re¬ 
sistance l5, 6,) it offers to its passage. In a very long 
circuit, such as a telegraph line, the action of the cur¬ 
rent will necessarily be feeble, and the coil is, there¬ 
fore, made of fine wire, which occupies little space, and 
allows many layers to be wound on without too greatly 
increasing the distance from the cores, while its resist¬ 
ance is too small in proportion to the rest of the cir¬ 
cuit to reduce the strength of the current materially. 

37. When, however, the circuit is very short, coarser 
wire is employed in the coil. A fine wire would add 
to the resistance of the circuit more than would be 
made up by the effect of an increased number of turns, 
for even a very few layers would double the resistance 
of the circuit. 

The former is frequently called an intensity , and the 
latter a quantity magnet. 



















ELECTRO-MAGNETISM. 


23 


38. Iron does not acquire its full magnetism instan¬ 
taneously, and the act of demagnetization also requires 
time, but is effected more rapidly than magnetization. 
The greater the tension of the battery the more rapidly 
the iron acquires its magnetism ; therefore, if very 
rapid action is required, even on a short circuit, a num¬ 
ber of cells of battery must be used. 

It has also been ascertained by experiment that an 
electro-magnet with short cores, will acquire and lose 
its magnetism with much greater rapidity than one with 
long cores, but in other respects similar. 


v '» 


CHAPTER III. 


TELEGRAPHIC CIRCUITS. 

39. A Telegraphic Circuit consists of one or more 
batteries, the line wire, the instruments and the earth. 
When the circuit is very short a return wire is fre¬ 
quently used instead of the earth. 

40. Owing to the immense rapidity with which the 
electric force is propagated throughout a circuit, any 
effect which can be produced at hand can be produced 
in any other part of a circuit, however distant, at the 
same instant of time, subject to a diminution of force, 
arising from causes which diminish the quantity of elec¬ 
tricity, or the force of the current before its arrival at 
the distant end, thus weakening its effect. The princi¬ 
pal causes of this diminution are the resistance of the 
circuit and defective insulation, in consequence of which 
a portion of the current escapes from the line to the 
earth, and returns without traversing the distant por¬ 
tion of the circuit. 

41. The effective force of the current leaving the bat¬ 
tery depends upon two things—the tension of the bat¬ 
tery, which sets the current in circulation, and the 
resistance the current encounters in traversing the cir- 
cuit. 

42. Resistance of the Circuit. —This depends upon 
the length and size of the conductor, and the material 
of which it is composed. In an ordinary telegraphic 
line wire the resistance is in direct proportion to its 
length, and also in inverse proportion to its weight per 
mile. Thus, 150 miles of No. 8 wire will conduct as 
well as 100 miles of No. 10 wire, and as great an effect 
can be produced at its remote end with a battery of 
equal tension. There is, therefore, a great advantage 






TELEGRAPHIC CIRCUITS. 25 

in using the larger sizes of wire in the construction of 
lines intended to be worked in long circuits. 

43. Electrical Measurement.— In order to institute 
a comparison between the resistances of different cir¬ 
cuits, etc., a standard has been fixed upon by the Brit¬ 
ish Association, called the Ohm, which is equivalent to 
about tV of a mile of galvanized No. 9 iron wire, such 
as is usually employed in the construction of telegraph 
lines. This standard unit of resistance is now made use 
of by the English electricians. 

44. Resistance Coils. —As no battery is constant in 
its power, and no magnet uniform in its strength, neither 
of these can be made use of as an accurate basis of com¬ 
parison. Resistance coils , composed of wire of certain 
alloys of metals, carefully prepared, have been found 
not to vary t.o outsit in eight years. The only variation 
is that due to difference in temperature, which may be 
readily calculated and allowed for when necessary. 

It will, therefore, be understood that the ohm is a unit 
of resistance in the same manner that an inch is a unit 
of length, or a pound a unit of weight. 


LINE 



45. A Telegraphic Circuit, in its simplest form, is 
shown in tig. 9. A and B represent two stations. The 
circuit may be traced as follows: From the + pole of 
the battery E to the keyK (52) and electro-magnet M, 
thence through the line L to the other station, electro¬ 
magnet M' and key K' to the earth at G-', and thence 
through the earth, as represented by the dotted line, to 
the — pole of the battery E. A continuous current will 














26 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


therefore flow through the circuit as long as it remains 
uninterrupted, and the armatures of the electro-magnets 
M and M' will be attracted by the cores, but if the cir¬ 
cuit be broken by means of one of the keys, Iv or K', 
both electro-magnets will be demagnetized. Thus, the 
breaking of the circuit at either station affects the elec¬ 
tro-magnets of both, as they are in the same circuit. 

46. The Earth Circuit. —In thus using the earth as 
part of the circuit, it is found that it offers, practically, 
no resistance to the passage of the current. Although 
comparatively a poor conductor, it is an infinitely large 
one in proportion to the wire, and, therefore, its resis¬ 
tance is not appreciable (42). 

47. Arrangement of Batteries. —In practice it is 
usual to divide the battery E into two parts, placing 
half at each end of the line, for reasons which will 
hereafter appear. It is important, however, when this 
is done, that the positive pole of one battery should 
be connected with the negative pole of the other, other¬ 
wise they would neutralize each other, and no effect 
would be obtained. In such a case the batteries are 
6aid to be reversed. 

48. Intermediate Stations. —It is evident that in¬ 
termediate stations may be introduced at any point 
upon the line shown in the above figure, each being 
provided with an electro-magnet and key, forming part 
of the circuit, and that the breaking and closing of the 
circuit at any of these points will affect all the electro¬ 
magnets through which it passes, in the same manner 
and at the same instant of time. 

Any desired number of intermediate stations may 
be placed upon a line until the combined resistance of 
their electro-magnets reduces the strength of the cur¬ 
rent below that required for the convenient working of 
the circuit. 

49. The Morse System. —The principle of the Morse 
system of telegraphy consists in conveying arbitrary 
signals by means of the magnetization and demagneti¬ 
zation of an electro-magnet, by the alternate breaking 






TELEGRAPHIC CIRCUITS. 


27 


and closing of a voltaic circuit in the manner above ex¬ 
plained. The conventional alphabet used in America 
for this purpose is given in another part of this work. 

50. Other Telegraphic Systems. —The type print¬ 
ing telegraph, employing the “ Combination” instrument 
of Phelps, is the only system other than the Morse now 
in use upon the public lines in the United States. The 
limited extent to which it is employed renders it unneces¬ 
sary to give a detailed description of its construction 
and mode of operation in a work of this kind. The 
electro-chemical telegraph of Bain, and the beautiful 
type-printing instruments of House and Hughes, were 
formerly extensively employed in this country. The 
former has now given place to the Morse, while the two' 
latter have been superseded by the equally rapid and 
more simple and effective instrument of Phelps. 

In addition to these, the magneto-electric dial instru¬ 
ment of Edmands & Hamblet, and the electro-magnetic 
alphabetical instrument of Chester are finding exten¬ 
sive employment upon private lines, where extreme 
rapidity of transmission is not required, thus rendering 
the employment of skilled operators in such cases un¬ 
necessary. 



CHAPTER IY. 


THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 

51. The Morse Telegraphic Apparatus consists of a 
signal key for breaking and closing the circuit, and an 
electro-magnet, the armature of which is attached to a 
lever carrying a steel point or style, which embosses a 
mark upon a narrow strip of paper, moved uniformly 
along by clock-work. As long as a current continues 
to flow through the coils of the electro-magnet the 
armature is attracted, and a mark is made upon the 
moving paper. As soon as the circuit is broken the 
armature ceases to be attracted, and is withdrawn from 
contact with the paper by means of a spring. The 
duration of the current, and consequently the length of 
the mark, depends upon the duration of the contact made 
by the key. 


D 



Fig. 10. 


52. The Morse Signal Key is shown in fig. 10A' It 
consists of a brass lever, A, four or five inches in length, 
which is hung upon a steel arbor, G, between adjustable 
set screws, I) l), in such a manner as to allow it to 
move freely in a vertical direction. This movement, 
however, is limited in one direction by the anvil C, and 
in the other by the adjustable set-screw, F. 

* The drawings of the signal key. register and relay (figs. 10,11 and 12), are from 
instruments manufactured by Bradley. 















































♦ 






Manufactured by L. 0. Tillotson tfc < o., New York, 























































































































THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


29 


One. wire of the main circuit is connected to the 
metallic frame of the key, and the other to the anvil, C, 
which is insulated from the frame. These connections 
are made by screws passing up through the table from 
beneath. The lever is provided with a knob of vulcan¬ 
ite, B, by means of which it may be pressed down by 
the finger of the operator, bringing the lever in contact 
with the anvil, and thus closing the circuit, precisely as 
if the wi res themselves had been brought together. The 
points of contact between the lever and the anvil are 
made of platina, as ordinary metals would be fused by 
the passage of the electric spark when the circuit is 
broken. A spring beneath the lever restores it to its 
original position when the pressure of the operator's 
finger is withdrawn. When the key is not in use the 
circuit is completed by bringing the lever of the cir¬ 
cuit closer , H, into contact with the anvil, C. 

• ' 



C. WHICH T.N. Y. 

Fig. 11. 

53. The Morse Register. —Fig. 11 represents the 
recording apparatus, usually termed a register , which is 
made in several different forms, all involving the same 
principles. M is the electro-magnet, the two ends of 
the wire forming the coils being carried to the terminal 
binding screws on the base, one of which is shown at 
s, to which the conducting wires are attached. Above 
the electro-magnet is seen the armature attached to 
the lever L, which moves upon an arbor at d. The op¬ 
posite extremity of the lever carries a steel point, p. 

















































30 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPn. 


The strip of paper passes through the guide g and be¬ 
tween the grooved rollers r r , which are moved by 
a train of wheels driven by a weight attached by a cord 
to the drum, W. 

When the armature is attracted by the magnet the 
style p is brought forcibly in contact with the paper, 
moving above it upon the grooved roller, and a raised 
line is embossed upon it corresponding in length to the 
time the armature remains attracted. A spring ad¬ 
justed by the nut n withdraws the lever when the at¬ 
traction ceases. The movement of the lever is limited 
by the adjustable screw, m. The screw c regulates the 
pressure of the rollers upon the paper, and the clock¬ 
work is started and stopped by the brake a. The 
weight is wound up occasionally, as required, by the 
operator. 

54. The Morse instrument is worked either by the 
main line current or by relay . For a distance not ex¬ 
ceeding 20 or 30 miles, a register, whose coils are 
wound with No. 30 copper wire, may be worked by the 
line current, if the line be well insulated (57). 

55. When the insulation is defective, or the circuit 
so long that its resistance renders the current too weak 
to work a register direct, as is usually the case with 
telegraph lines, it becomes necessary to employ a re¬ 
ceiving magnet or relay , which brings a local battery 
(11) into action at the receiving station, the current of 
which operates the register. 



Fig. 12. 

56. The Relay Magxet. —The construction of the 
relay is shown in fig. 12. M is the electro-magnet, 



























V 
























































































































THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


31 


which is placed in a horizontal position, and is movable 
by means of the screw a. The coils of the magnet are 
of fine wire, usually from No. 30 to No. 36 in size, of 
great length and closely wound.* The ends are con¬ 
nected to the line circuit by the binding screws, m m . 
The armature lever b is connected with the binding: 
screw l by a wire carried underneath the base of the 
instrument. A platina point, c, on the armature lever, 
is brought in contact with a similar point on the end of 
the screw cl whenever the armature is attracted by 
the magnet, the screw being in metallic connection with 
the binding screw by means of the frame of the appa¬ 
ratus and a wire beneath the base. One of the screws, 
11', is connected to one pole of the local battery (11), 
and the other to the other pole, embracing the register 
magnet in its circuit. Therefore, whenever the arma¬ 
ture is attracted by the force of the main current acting 
upon the relay magnet, the circuit of the local battery 
is completed through the register. As the relay is con¬ 
structed with great delicacy, a feeble line current is 
enabled to actuate a register powerfully through the 
intervention of a local battery. 

The movement of the armature is regulated to corres¬ 
pond with the varying strength of the line current by 
means of the adjustable spiral spring /. The magnet 
may be also set at any required distance from the arma¬ 
ture by means of the screw a, which is cut with a right 
and left hand thread, passing through the soft iron bar 
connecting the two cores, and also through the support¬ 
ing post in the rear of the coils. The latter slide through 
openings in the upright metallic plate which supports 
the adjustable platina pointed screw cl. 

* In the instruments manufactured by Dr. Bradley the helices or coils of the 
electro-magnets, instead of being composed of silk insulated copper wire, as de¬ 
scribed in § 34. are made of naked wire, ingeniously wound by accurate machinery 
in such a manner that the convolutions are separated from each other by a space 
of 1-600 to 1-S00 of an inch, the several layers being insulated frorp each other by 
thin paper. It is claimed that, by this method of winding, a coil of a given length 
and gauge of wire, and, consequently, of a given resistance, can be made of much 
less diameter than is possible with silk insulated wire, while, at the same time, the 
number of convolutions will bo increased as well as the power of the electro- 


32 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


Fig. 13 represents a Pocket Relay , as it is usually 
termed, although it is properly a main line sounder (57). 



Fig. 13. 


This is provided with a key, as shown in the figure, the 
whole being conveniently and compactly arranged to fit 
into an oval case four or five inches long, which may be 
carried in the pocket It is an extremely convenient 
apparatus for line repairers. The cut shows the ar¬ 
rangement manufactured by the Messrs. Chester. 



57. The Sounder. —In many of the larger telegraph 
offices the recording apparatus is dispensed with, and 
the communications read by the sound of the armature 
lever. In that case the Sounder (fig. 14) is employed in 
the place of the register, the connections of the wires 
being arranged in precisely the same manner. The 
Sounder consists simply of the electro-magnet, arma- 















































































THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


ture and lever, fixed upon a base.* The coils are usu¬ 
ally wound with No. 23 wire. 

Main Line Sounders are used in some offices, which 
enables the operator to dispense with the local battery. 
The coils are wound with fine wire, usually No. 30, and 
are frequently made somewhat larger than those of the 
relay. A common form of this instrument is known as 
the ‘'Box Sounder.” The lever, striking upon a hollow 
wooden box containing the magnet, gives a sound that 
may easily be distinguished by the operator under ordi¬ 
nary circumstances. 



Fig. 15. 


Fig. 15 ( S . F. Day & Co.) shows an excellent form of 
Main Line Sounder. The parts of the instrument are 
mounted upon a metallic plate, the centre of which is 
raised slightly above the base, so as to form a bridge, as 
shown in the cut. The armature lever is of steel, and 
the whole arrangement is well adapted to increase the 
sound of the lever as much as possible—a feature of great 
value in working with weak currents or on badly insu¬ 
lated lines. These instruments are also made in seve¬ 
ral other forms, and various devices for increasing the 
sound of the lever are made use of. On many lines 
they arc found to answer as well as the usual arrange¬ 
ment, employing a relay and local battery. 

* Tho instrument shown in the figure is from tho manufactory of C. T. & J. N. 
Chester. 3 













34 


MODERN PRACTICE OF THE ELECTRIC TELE.GRAPII, 


For circuits of moderate length a Main Line Register 
(fig 16), manufactured by Day & Co., has been employed 
with excellent results. 



Fig. 16. 


58. Arrangement of a Terminal Station. —Fig. IT 
is a diagram showing the arrangement of wires, batteries, 



and iinstruments for one of the terminal stations of a 




















































































RELAY MAGNET. 


LOCAL SOUNDER. 




CONBINATION MAIN LINE INSTRUMENT. 

Manufactured by L. G. Tdlotson Co., New York. 















































































































































































































































THE MOUSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


35 


line. The line wire L first enters the lightning arrester 
X, and passes thence through the coils of the relay M 
by the binding screws, 1, 2, and thence to the key K, 
main battery E, and finally to the ground at G-. The 
local circuit commences at the + pole of the local bat¬ 
tery E' and through the platina points of the relay by 
the binding screws, 3, 4, thence through the register 
or sounder coils, S, and back to the other pole of the 
battery. 



59. Arrangement of a Way Station. —Fig. 18 
shows a plan of the instruments and connections at a 
way station. The line enters at L, passes through the 
lightning arrester X (70), and thence through the relay 
M, key K, and back to the lightning arrester, and 
thence to the next station by the line L'. The arrange¬ 
ment of the local circuit is the same as in the last figure. 
The button C, arranged as shown in the figure, is called 
a “ cut-out'’ 1 (62). When turned so as to connect the two 
wires leading into the office, it allows the line current 
to pass across from one to the other without going 
through the instruments. The instruments should 
always be cut out by means of this apparatus when 
leaving the office temporarily, or for the night, and 




















































36 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


also during a thunder storm, to avoid damage to the 
apparatus. Fig. 21 shows a better arrangement. 

The Ground Switch , Q (63), is used to connect the 
line with the earth on either side of the instruments at 
pleasure. It is only used in case of accidents or inter¬ 
ruptions on the lines, as will be hereafter explained. 

' GO. Adjustment of the Apparatus. —The princi¬ 
pal difficulties which the operator is liable to meet with 
in working the Morse apparatus arc as follows : 

1. When the paper in the register does not run freely 
from the reel on which it is held, or sticks in the guides 
from irregularity in width, or if the style is adjusted to 
indent the paper too deeply, the paper moves irregu¬ 
larly, shortening dashes into dots, and causing dots to 
run together. 

2. The style should be adjusted so as to move freely 
in the groove of the upper roller, or the marks will be 
more or less indistinct. If it is completely out of the 
groove, no marks will be produced. These faults gene¬ 
rally arise from too much end play in the pivots of the 
lever, or from the pivot screws working loose. When 
the lever works too loosely in its bearings, irregular 
dashes, too deep at their commencement, and tapering 
off to nothing, will be produced. 

Residuary magnetism sometimes causes the armature 
of the electro-magnet to stick . This will always hap¬ 
pen if the armature is allowed to touch the poles of the 
magnet. The screw stop should therefore be adjusted 
so as to prevent the armature from approaching • too 
closely to the poles of the magnet. The upper screw 
stop, which regulates the play of the lever, should be 
adjusted so that the movement is just sufficient to with¬ 
draw the style from contact with the paper. 

3. If the paper runs between the rollers “ crooked, ” 
the pressure of the upper roller upon the paper is 
greater at one end than the other. This pressure is re¬ 
gulated by two springs, one on each side of the instru¬ 
men t, and they should be made as nearly equal in pres¬ 
sure as possible. 



THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 37 

4. When the signs are confused the relay requires 
adjustment to suit the strength of the current. 

5. If the relay moves by the action of the line cur¬ 
rent, and the register or sounder does not act, the fault 
is somewhere in the local circuit. If the register does 
not work when the relay is moved by the linger, the 
local circuit is certainly at fault, either from weakness 
of the local battery, a loose connection, a broken wire, 
or dirt between the platina points of the relay. The 
latter should, when too much corroded, be cleaned care¬ 
fully with emery paper, taking care to remove as little 
of the platina as possible. 

6. The sticking of the key, which sometimes occurs, is 
caused either by the platina points becoming oxidized 
and dirty, or by small particles of metal and dirt collect¬ 
ing behind the circuit closer and about the anvil, caus¬ 
ing a partial connection when the key is open. 

7. It is very important that all the connections about an 
office should be firmly screwed up. Neglect of this pre¬ 
caution is a very prolific cause of trouble upon a tele¬ 
graph line. 

8. In rainy weather, or when the insulation of the 
line is defective from any cause, the cores of the relay 
must be withdrawn to a greater distance from the ar¬ 
mature, to avoid the influence of the residual magnet¬ 
ism, caused by the escape of the “current” from the 
line. This is called “adjusting” the instrument, and is 
one of the most important of an operator's duties, re¬ 
quiring great judgment and skill during unfavorable 
weather and on poorly insulated lines. The key should 
never be opened without carefully adjusting the relay, 
to be sure that no other offices are using the line. 

SWITCHES on COMMUTATORS. 

Gl. These are emplojmd for the purpose of connect¬ 
ing one circuit with another, for dividing a circuit into 
two parts, or in short, for any purpose where it is neces¬ 
sary to alter the connections of a line or circuit. 

62. Fig. 19 shows the simple Button or Circuit Closer , 


38 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


which is usually employed as a ‘‘cut out” (58). The 
base A is of wood or hard rubber. The brass lever, B, 
when in the position shown in the figure, forms an elec¬ 
trical connection between the metallic studs C C, which 



are continuous with the screws, D D, passing through the 
table and terminating in binding screws, to which the 
wires are attached. The spring F, pressing against 
the lever, insures a firm contact with the studs. This 
circuit closer is sometimes, for special purposes, made 
with four connections instead of two. 













TIIE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


39 


A is attached to a wire leading to the earth, and the two 
studs, B, C, are connected to the line wire on each side 
of the instruments. 



64. The Plug Switch is shown in fig. 21. This ar¬ 
rangement consists of a brass spring, brought very 
firmly against a stationary pin. A wedge or plug made 
of two pieces of brass, separated by an insulating mate¬ 
rial, is made in the form shown, to admit of insertion 
between the spring and the pin. The wires leading to 
the instrument are attached to this wedge by flexible 
conductors. When the wedge is inserted, the line cur¬ 
rent is diverted through the instrument, but is not in¬ 
terrupted. The instrument may readily be withdrawn 
from the line by taking out the wedge, the spring in¬ 
stantaneously closing the main circuit. This arrange¬ 
ment is found extremely useful in connecting batter¬ 
ies as well as instruments. At a way station it is 
preferable to a simple cut-out, for the reason that the 
apparatus is entirely disconnected from the circuit when 
the wedge is withdrawn (59). 

65. The Universal Switch, for the use of offices 
having a considerable number of wires, is constructed 














































































40 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


in several different forms, although the principle in¬ 
volved is nearly the same in each. Fig. 22* represents 


ABC D E F 



Fig. 22. 


the arrangement most generally used, which is known 
as the Culgan Switch, from the name of its inventor. 
The upright straps of brass, A, B, C, D, E, F, are fixed 
upon a slab of hard wood, or other non-conducting ma¬ 
terial, and provided with binding screws at their upper 
extremities, for the reception of the line wires. The 
binding screws, I, IT, III, IV, Y, YI, are in electrical 
connection with the horizontal rows of buttons, by wires 
underneath the board, not shown in the figure. Thus, 
any wire attached to one set of binding screws may 
readily be connected with any wire attached to the other 
set, by simply turning the appropriate button. A row 
of metallic pegs, x x', are so arranged that either of the 
upright straps may be separated into two parts by the 
withdrawal of the peg belonging to it, as shown at x. 
The object of this device will be explained hereafter. 

This switch may be made of any size and with any 
number of connections, depending upon the number of 
lines it is designed to accommodate. The wires maybe 
attached to it in a number of different ways, the parti- 

* L. G. Tillotson & Co., New York. 




































































































































THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


41 


cular arrangement adopted in each case depending upon 
the nature of the changes required to be made. 

66. Arrangement of the Connections. —The switch 
shown in the figure, placed at a way station , could be 
arranged to accommodate three through wires, and an 
equal number of instruments, providing for all the ne¬ 
cessary changes. The arrangements in this case would 
be as follows : Connect line wires Nos. 1, 2 and 3, east , 
with A, B and C ; 1, 2 and 3, west , with D, E and F. 
Instrument No. 1 to I and II, No. 2 to III and IV, 
No. 3 to V and VI. Turn the buttons so as to connect 
A with I and D with II. The circuit of No. 1 wire will 
then enter at A, go to instrument No. 1 via I, returning 
to II, and thence going out at D. The other instru¬ 
ments may be connected at pleasure in the same man¬ 
ner. If it is desired to connect a circuit through , for 
instance No. 1, leaving the instrument out of circuit, it 
is done by turning the buttons so as to connect both A 
and D to the same horizontal wire, either I or II. By 
a little study it will be seen that any wire cast may be 
connected with an} r other wire west, with or without 
any desired instrument, at pleasure. The ground wire 
is attached at VII, and may be connected with any line 
wire east or west at pleasure. 

67. The same switch, placed at a terminal station , 
would provide for six wires, by connecting them as be¬ 
fore to the screws A, B, C, D, E, F, and the instruments 
to I, II, III, IV, V, VI. The wires of a loop (87) may 
be connected to I and II in place of the instrument, 
and may be put in circuit with any wire by turning the 
buttons connected with I and II both on to the corres¬ 
ponding strap, which is then divided by withdrawing 
the peg, forcing the current to pass through the loop. 
Extra sets of buttons for loops are usually provided 
when the switch is intended for a terminal station, which 
can be used without diminishing the capacity of the 
switch for other purposes. 

68. Jones’ Lock Switch is employed for the same 
purposes, and connected in the same manner as the one 



42 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


last described, but the connection between the vertical 
and horizontal wires is made by a metallic peg, provided 
with a spring, as shown in fig. 23 {Chester). This ar¬ 
rangement entirely obviates the danger of imperfect 
connections, from the loosening of buttons, etc., which 
is sometimes a source of trouble in the Culgan Switch. 



Fig. 23. 


It is also cheaper and much more compact; a matter of 
some importance in arranging for the accommodation of 
a large number of wires. 

69. There are other forms of switches designed for 
special purposes, which it is unnecessary to describe in 
a work of this kind. Those already referred to are all 
that are generally required in fitting up a telegraph 
station. 


LIGHTNING ARRESTERS. 

70. The danger of injury to the instruments and 
operators at a telegraph station, by atmospheric elec¬ 
tricity, is usually guarded against by the use of an 
apparatus termed the Lightning Arrester , which is con¬ 
structed in accordance with the well established fact 
that this kind of electricity, being possessed of enor¬ 
mous intensity, prefers a short route through a poor 
conductor to a longer one through a good conductor, 
while the comparatively low intensity of the voltaic 







THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


43 


current, used for telegraphic purposes, confines it to 
the conducting wires. 

71. The Plate Arrester. —The arrester most usu¬ 
ally employed upon the telegraph lines in this country 
consists of a flat plate of brass, about five or six inches 
in length, which is attached to the “ground wire.” 
Other plates of brass rest upon this, being separated 
from it by a thin sheet of insulating material. These 
last mentioned plates are provided with binding screws, 
for the attachment of the line wires. Any surplus 
charge of atmospheric electricity, entering by the line 
wires, forces its way through the insulating material into 
the ground plate, and is thus carried off to the ground 
without injuring the apparatus. The form of arrester 
supplied by the Messrs. Chester is shown in fig. 24; 



Fig. 24. 


The plates in connection with the line wires are 
firmly held in their places by a wooden cross piece, 
secured by screws at each end, as shown in the cut. A 
thin sheet of gutta percha, or paper, is used to separate 
the plates. When paper is used it should be saturated 
with paraffine. Mica is, perhaps, better than cither, as 
it is not carbonized by the passage of the spark, as pa¬ 
per sometimes is, so as to form a ground connection. 
The manner in which the arrester is connected with the 
wires leading into an office will be seen by reference to 
fig. 18, where the two line wires, L and L', arc attached 
to the two upper plates of the arrester, X, while a wire 
leading to the ground at Gf is attached to the lower plate. 

72. Bradley’s Arrester. —Another form of arrester, 

























44 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


designed by Dr. Bradley, is shown in fig. 25, and lias 
recently been quite extensively employed, with excel¬ 
lent results. 



Fig. 25. 


It depends for its action upon the well ascertained 
fact that lightning always passes fro’m a point to a plate 
with great facility. The line wires leading into the 
office are attached to the metallic plates A and B by 
means of binding screws beneath, the ground wire being 
attached in the same manner to the plate C. Platina 
tipped screws, 1, 2, 3, 4, are tixed to each plate, and 
are adjusted so as to come nearly in contact with the op¬ 
posite plate. As lightning occasionally passes from the 
earth to the clouds, as well as from the clouds to the 
earth, this arrester is so arranged as to facilitate its 
passage in either direction. The buttons, F F, are so 
arranged that the apparatus serves for a “ cut-out” and 
a “ground switch” as well as an arrester. Its appli¬ 
cation to these purposes will be at once understood by 
an inspection of the cut. This form of arrester is 
peculiarly well adapted for the protection of cables, or 
any situation where it is exposed to accidental damp¬ 
ness, as it is much less apt to interfere with the work¬ 
ing of the line in such cases than the plate arrester pre¬ 
viously described. 

73. Lightning arresters must always be kept free 
from dampness and dirt, as far as practicable. Much 
annoyance often arises from neglect of this precaution, 
as moisture between the plates will often cause a seri¬ 
ous escape, greatly interfering with the working of the 
line. This difficulty is especially liable to occur where 
the arresters are used for the protection of submarine 
cables. A flash of atmospheric electricity also fre- 
























THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


45 


quently carbonizes the paper between the plates, or 
fuses the metal, so as to permanently connect the 
ground and the line. Consequently, the lightning ar¬ 
resters should be frequently taken apart and examined. 
This should invariably be done after a thunder storm. 


REPEATERS. 

74. When the length of a telegraphic circuit exceeds 
a certain limit, depending upon the insulation, the size 
of the conductor, the number of instruments in circuit, 
etc., the line current becomes so enfeebled, even when 
large batteries are employed, that satisfactory signals 
cannot be transmitted. In such cases it was formerly 
customary to re-write the messages at some interme¬ 
diate station, but this duty is now usually performed by 
an apparatus called a repeater. The principle of this 
arrangement consists in causing the sounder or register 
connected with one circuit to open and close the circuit 
of another line by an action similar to that of a relay 
(56). Repeaters are also often used for connecting one 
or more branch lines with a main line, for the purpose 
of transmitting press news, etc., simultaneously to dif¬ 
ferent places. This enables all the stations in connec¬ 
tion to write to each other as readily as if they were 
situated upon the same circuit. 

Since the general introduction of repeaters it has 
become quite practicable to telegraph direct between 
places situated at very great distances from each other. 
It is not uncommon, at the present day, to work direct 
through four or five thousand miles of continuous line 
by the aid of these instruments with almost as much 
facility as if it were one continuous circuit. On one or 
two occasions the stations at Heart's Content, New¬ 
foundland, and San Francisco, California, have been 
placed in direct communication with each other, the 
operators at these widely separated points conversing 
with each other across the entire breadth of the contb 
nent without the slightest difficulty. 


46 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


75. Wood’s Button Repeater. —This is the simplest 
arrangement of this kind now in use. Fig. 2G shows 



Fig. 26. 


the most convenient and serviceable form in which the 
button or switch, and its connections, can be arranged 
for the purpose of changing the circuits. The instru¬ 
ments, batteries, &c., are shown in outline, for conve¬ 
nience of explanation. M and M' are the eastern and 
western relays, S and S' the eastern and western soun¬ 
ders. The local connections are not shown, but are run 
as usual. The eastern and western main batteries are 
shown at B and B', and are placed with opposite poles 
to the ground, at the repeating station, so that when the 
line is put “ through” the two batteries will coincide. 

By means of this arrangement the following result 
may be obtained : 

I. Two distinct and independent circuits. The lever L 
remaining in the position shown in the drawing (marked 
1), and the button at 4, closed. 

II. A through circuit. The lever L remains as before, 
but the button at 4 is opened , throwing off the ground 
connection between the two batteries, B and B'. 

III. Two distinct circuits arranged for repeating. The 
button at 4 is closed. If the lever L be placed in the 














































THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


47 


position indicated by the figures 2, 2, the eastern soun¬ 
der repeats into the western circuit. If the lever is 
changed to 3, 3, the western sounder repeats into the 
eastern circuit. The operator in charge of a button 
repeater will find his duty very simple if lie governs 
himself by the following 

Rule. —When either sounder fails to work coincident 
with the other, turn the button instantly. 

In connecting up this apparatus, the arrangement of 
the poles of the main batteries above specified should 
be carefully borne in mind. It is also of the utmost 
importance that these batteries should be perfectly in¬ 
sulated from the ground, as the point at which the cir¬ 
cuit is open and closed is between the battery and the 
ground. Therefore, an escape occurring from the bat¬ 
tery to the ground will cause a residual current upon 
the main line, when the circuit is open at the repeat¬ 
ing points of the sounder, and thus interfere with its 
working. 

In cases where it is not required to work the two 
lines through in one circuit, the connections are ar¬ 
ranged differently from the plan shown in fig. 26, the 
main battery being placed in the circuit between the 
lever L and the ground G, instead of at B and B', as 
shown. In this case the switch 4 may be dispensed 
with altogether. 

76. The lever of the sounder moves through a certain 
space before closing the circuit of the second line, so 
that the duration of the current sent forward is shorter 
than that received from the transmitting station. A 
second repeater shortens it still more, so that the dots 
cease to be repeated, and are frequently lost altogether. 
The sending operator must therefore transmit the sig¬ 
nals more firmly , as it is termed ; that is, increase the 
length of the key contact, especially when sending dots. 
For the same reason, the sounder levers in a repeating 
apparatus should be adjusted to have as little motion as 
possible. 

77. Hicks’ Automatic Repeater.— This arrangement 



48 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


dispenses with the attendance of an operator for the 
purpose of changing the circuits while working, the only 
attention required being to keep the relays properly 
adjusted. The principle of the apparatus is shown in 
fig. 27. 



The main circuits pass through the relay magnets M 
and M', thence to the repeating points / g and f g', 
attached to the opposite sounder levers respectively, 
and thence to the main battery and ground at G and 
G'. The platina points of the screws/and/' are placed 
uponU shaped springs, which, in a great measure, pre¬ 
vents the shortening of the signals referred to in the 
last paragraph. The local circuits are run through the 
relay points b and b' and the sounders R and R', on 
each side of the apparatus, in the ordinary manner, but 
to prevent confusion of lines, are omitted in the draw¬ 
ing. The “ extra local 7 ’ magnets, L and L' act upon 
armatures placed upon the relay levers a and a\ oppo¬ 
site to the regular armature. (See figure.) These 
extra local magnets are movable by means of the screws 
d d\ and the adjustment of the relays MM' is performed 
by means of these extra local magnets, the springs s s' 
not being used for this purpose. 

In the figure the repeater is shown in its normal 
position, with both circuits closed. The circuits of the 


































































































































































THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


49 


extra local batteries B B' (shown by dotted lines) pass 
through the sounder levers l l\ the screws p p', and 
thence respectively to the extra local magnets on the 
opposite side of the apparatus. These magnets must be 
so adjusted that their attraction is not sufficient to draw 
the armatures away from M M' unless the main circuit 
is broken. 

It will also be seen, by referring to the drawing, that 
when the main circuit is broken and the armature falls 
back on the point c, that the extra local magnet L is cut 
out . But the instant this happens the spring s draws 
the armature away again. As soon as the contact is 
broken at c there is a circuit through L, and the arma¬ 
ture is again drawn back to c. The tension of the 
spring s being but just sufficient to draw the armature 
away from c, the armature vibrates on the point c through 
such a small space, and with such rapidity, that the 
motion is invisible to the eye. On account of the ex¬ 
treme rapidity of these vibrations, it is impossible to 
close the main circuit at a time when the extra local 
magnet L is not cut out , and the armature will conse¬ 
quently obey the slightest impulse caused by the attrac¬ 
tion of the relay magnet. 

The working of the apparatus requires but little fur¬ 
ther explanation. If the western main circuit be broken, 
for instance, the armature lever a falls back and vibrates 
on the point c, as above described. The sounder lever 
l first breaks the circuit of the eastern extra local mag¬ 
net L', then that of the eastern main line, which passes 
through the relay M. The circuit through both L and 
M' being thus broken, the slight tension of the spring s' 
will hold the armature in its place, and prevent the 
local circuit through R, and consequently the western 
main circuit, from being broken. When the western 
circuit is again closed the reverse of these operations 
takes place. 

78. In using this repeater the springs s s' should be 
adjusted with the smallest possible amount of tension, 
just sufficient to hold the armature in place. When once 


50 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


adjusted they should he let alone. Care must be taken 
that none of the wires under or about the magnets touch 
any part of the brass. The extra local magnets, for 
example, may be cut out entirely in this way. The 
screws that adjust the extra local magnets should be 
oiled with fine oil to prevent wear and make their ad¬ 
justment easy. The extra local batteries must be kept 
of a uniform strength ; if they are allowed to become 
weak the instrument will be thrown out of adjustment. 

79. Milliken’s Repeater.— In the general arrange¬ 
ment of its connections this repeater somewhat resem- 
bl es that of Hicks’, but is more simple in principle. 
Fig. 28 is a plan of its connections. The main line 

L 


s 

-V/MW//- 1 


West 




111 

1 

1 

'T* - 




Fig. 28. 


wire from the west passes through the relay magnet M 
and the repeating points f g' of the opposite soun¬ 
der, and thence to the battery and ground at G'. The 
eastern line passes through M', / and g to G, in a simi¬ 
lar manner. 

The extra local magnets L and L' are arranged, as 
shown in the figure, so that when either of their arma¬ 
tures is released it is drawn back by the spring attached 
to its lever, bringing the latter firmly in contact with 
the armature lever of the corresponding relay. The 
extra local batteries are shown at B and B' the circuit 




































































































































THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


51 


of each being indicated by dotted lines. The ordinary 
local circuit through the relay and sounder is omitted, 
to avoid confusion in the diagram. 

If the main circuit be broken in the western wire, 
the relay M breaks the local circuit of the sounder R at 
b. The movement of the lever l of the sounder first 
breaks the extra local circuit aty>, causing the magnet 
L' to release the armature cl', which is drawn back by 
the spring s'against the top of the lever a, and, secondly, 
the eastern main circuit is also broken at /. g. The 
lever a is prevented from falling back when the circuit 
of M' is broken by the tension of the spring s', which is 
•so adjusted as to be greater than that of the spring ti. 
The apparatus on the right hand side of the repeater, 
therefore, remains quiet while the west is working, and 
vice versa, the current through M' being always restored 
before that through L' is broken, which is effected by 
the U shaped spring on the screw/. 

One of the principal advantages in the construction 
of Milliken s repeater consists in the fact, that any 
slight variation in the strength of the extra local circuit, 
from weakness of the battery or other causes, does not 
affect the adjustment of the relay magnets, as in the 
case with Hicks 7 repeater. The adjustment and action 
of the two magnets are entirely independent of each 
other, as will be seen by reference to the diagram. The 
relay levers also move more freely, being unencum¬ 
bered with extra armatures or other appliances. 

In this, as in the Hicks repeater, buttons are pro¬ 
vided, by means of which each line may be worked 
separately without interfering with the other, if desired. 

These are omitted in the drawing, to prevent confu¬ 
sion, but are arranged so that, when closed, one button 
forms a permanent connection between f and g, thus 
preventing the movement of the lever l from breaking 
the eastern main circuit, and another connects p and l, 
thus keeping the extra local circuit constantly closed, 
and the armature lever d' withdrawn from interference 
with a\ 


52 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


The same thing may be accomplished by causing the 
button to break the extra local circuit entirely, when 
the instruments are to be worked separately, and “ turn¬ 
ing down 77 the adjusting spring s' of the lever d'. It 
will, of course, be understood that the other side of the 
repeater is arranged in precisely the same manner. 



80. Bunxell’s Repeater.— The arrangement of the 
.main circuits in this repeater is exactly the same as in 
































































































































THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM 


53 


the ordinary “button repeater/ 7 and will be readily 
understood by reference to fig. 29. The eastern main 
wire enters at the right, passing through the repeating 
point, s', of the western sounder, S', and through the 
coils of the eastern relay, M, and thence to the main 
battery and earth at E. The western main wire is 
similarly connected on the opposite side of the instru¬ 
ment. In the button repeater (75) a switch is so ar¬ 
ranged as to form a connection, cutting out the repeat¬ 
ing points of the sounder on the opposite side, when 
either line is working, requiring a person to be con¬ 
stantly stationed at the instrument to make the neces¬ 
sary changes when two stations, on opposite sides of the 
repeater, are corresponding with each other. In Bun¬ 
nell’s repeater this duty is performed automatically by 
means of two “governor” or controlling magnets, Gr Gr, 
the action of which will be hereafter described. 

The eastern and western main circuits both being 
closed and the apparatus at rest, the course of the local 
circuit of the eastern instrument is as follows : From 
the local battery, L, through the coils of the eastern 
sounder, thence passing through the closed relay points 
at M, and returning to the other pole of the battery. 
The resistance of the governor magnet, Gr, prevents any 
appreciable portion of the current from passing through 
its coils, as long as the closed points of the relay, M, 
afford it a shorter route. If the local circuit be broken 
by the relay points at M, it is forced to pass through 
the coils of the sounder, S, and also of the governor, Gr. 

When a circuit of low intensity passes through the 
coils of two magnets, differing considerably in resistance, 
the attraction of the magnet having the least resistance 
is very small in comparison with that of the other. A 
practical application of this principle is made in this re¬ 
peater, by forming the helices of the governor magnet of 
finer wire than that of the sounders. The effect of this 
is, that when the local circuit is thrown through both mag¬ 
nets by the opening of the relay, that the armature of 
the governor magnet is attracted with considerable 


64 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


strength, while the magnetism developed in the sounder 
is not sufficient to move its armature, although the same 
current passes through its coils. This arrangement is, 
of course, the same on each side of the repeater, and by 
bearing it in mind the action of the instrument may be 
readily comprehended. 

When both main circuits are closed and the repeater 
at rest, the governor magnets remain open, being cut 
out by the points of the relays, which, as well as the 
sounders, are closed on both sides of the apparatus. If, 
now, we suppose the circuit to be opened by an oper- „ 
ator on the western main line, the armature of the relay, 
M', falls back, opening the sounder, S', and closing the 
governor magnet, G', as previously explained. This 
breaks the eastern main circuit at s', and also at a', as 
well as the circuit of the opposite governor magnet, G, 
at the point b. The breaking of the eastern main cir¬ 
cuit at S' opens the eastern relay, M, and consequently 
its sounder, S, but the circuit of the governor magnet, 

G, being broken at b\ it remains inactive, and the wes¬ 
tern main circuit is complete through the points, a , 
although broken at the point, s, by the opening of the 
sounder, S. Upon the closing of the western main 
circuit this action is reversed, and the apparatus re¬ 
sumes its original position. If the eastern main circuit 
be opened the same action takes place, but on the 
opposite side of the repeater. 

In most repeaters hitherto constructed one side of the 
apparatus remains silent while the opposite side is in 
action, but in this one the relays and sounders on both 
sides work together, the points, a, a, on the armature 
of the governor magnets acting automatically in the 
same manner as the switch of a button repeater, when 
moved by the hand of the operator. 

81. An advantage claimed for this repeater is, that 
both sides of the apparatus work together, affording the 
operator in charge a better opportunity to know how 
both lines are working. The extra local batteries are 
dispensed with, and the relay levers are not encumbered 


TIIE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


55 


with extra armatures and other appliances. The ad¬ 
justments required are the same as in a simple relay and 
sounder. 

82. Various other repeaters have been contrived, and 
to some extent adopted in this country, but as those we 
have described are much more extensively used than 
any others, it has not been deemed necessary to describe 
the others in a work of this kind. 

83. Combination Locals. —In offices containing a 
number of instruments, a single local battery is fre¬ 
quently employed to operate all the sounders in the 
office. Such an arrangement is called a combination 
local. The best way of making the connections is shown 
in fig. 30, in which the instruments arc represented at 



Fig. 30. 


I, II, III and IV. The local battery is shown at E. 
The common conductors, a and b , should be of large 
copper wire, say No. 12 or 14. If the ordinary Daniell’s 
battery is used for this purpose, the cells should be con¬ 
nected for quantity , as shown in the diagram, and not 
in a single series. Every sounder in the combination 
should have the same size and amount of wire in its 
coils, as nearly as possible, in order to secure the best 
results. 

84. Another plan is to use separate locals, a wire 
being run from one pole of each local to its correspon¬ 
ding instrument, the opposite poles of the batteries, and 
the instrument wires being all connected to a common 
return wire. 

85. These combination locals are very objectionable, 
however, and their use should be avoided wherever 

















56 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


possible. The iron cores in two different relays may 
happen to be in connection with the silk covered wire 
with which they are wound, a circumstance which fre¬ 
quently occurs. In such a case, if the two armatures 
chance to touch the poles of their respective relays, a 
metallic connection, technically called a cross , is made 
between the two main lines. Again, if these two relays 
are at a terminal station, and in connection with two 
main batteries, with opposite poles to the ground, the 
combined force of both batteries is thrown on short 
circuit, through the local return wire, burning the re¬ 
lays, exhausting the batteries, and interfering with the 
operation of every wire connected with them. The 
cause of these troubles being somewhat obscure, it might, 
for a considerable time, escape detection. 

86. Local Circuit Changer. —In offices containing 
two sets of instruments on different circuits, it is often 
desirable to change them. A simple arrangement for 
this purpose it shown in lig. 31, in which the relays are 



represented at M and M'; S and S' are the sounders or 
registers, E and E' are the local batteries. B is a simple 
button or circuit closer (62), having four connecting 
points, 1, 2, 3, 4. When the button is in the position 
1, 2, as shown in the figure, the relay M works the 
sounder S, and the relay M' the Sounder S'. By 
changing the position of the button to 3, 4, S is worked 
by M' and S' by M. This simple arrangement is often 
very convenient in railway stations, where a sounder 
may be placed on one circuit and a register on the 
other, so that an operator who is unable to read by 
sound can instantly shift the register upon either line 
at pleasure. 






























THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 


57 


TECHNICAL TERMS USED IN THE TELEGRAPH SERVICE. 

87. Line. —The wire or wires connecting one station 
with another. 

Circuit. —The wires, instruments, &c., through which 
the current passes from one pole of the battery to the 
other. 

Metallic Circuit. —A circuit in which a return wire is 
used in place of the earth. 

Local Circuit. —One which includes only the appa¬ 
ratus in an office, and is closed by a relay. 

Local. —The battery of a local circuit. 

Loop. —A wire going out and returning to the same 
point, as to a branch office, and forming part of a main 
circuit. 

Binding Screws or Terminals. —Screws attached to 
instruments for holding the connecting wires. 

To Cross-connect Wires. —To interchange them at an 
intermediate station, as in § 117. 

To put Wires straight. —To restore the usual arrange¬ 
ment of wires and instruments. 

To Ground a Wire , or put on Ground. —To make a 
connection between the line wire and the earth. 

To Open a Wire. —To disconnect it so that no current 
can pass. 

Reversed Batteries. —Two batteries in the same cir¬ 
cuit with like poles towards each other. 

To Reverse a Battery. —To place its opposite pole to 
the line ; or, in other words, interchange the ground and 
line wires at the poles of the battery. 

Escape. —The leakage of current from the line to the 
ground, caused by defective insulation and contact with 
partial conductors. 

Cross. —A metallic connection between two wires, 
arising from their coming in contact with each other, or 
from other causes. 

Weather Cross. —The leakage of current from one 
wire to another during rainy weather, owing to defec¬ 
tive insulation. 















CHAPTER V. 


INSULATION. 

88. A telegraph wire suspended on poles is attached 
to insulators, to prevent the escape of the current to the 
earth at the points of support. Insulators should be 
regarded in the light of conductors , whose value depends 
upon their resistance to the passage of the current. 

89. The insulation of a line is never perfect, even in 
the digest weather. There is a leakage at every sup¬ 
port, which is greatly increased when the surfaces of the 
insulators are damp, especially if covered with smoke 
or dirt. Experiments show that soot will destroy the 
surface insulation of the best insulators, even when 
exposed to the cleansing action of the rain. This evil 
is confined, however, principally to cities, and does not 
manifest itself to nearly so great an extent in the open 
country. 

90. Insulators, considered as conductors, follow the 
same law as other conductors. The less the diameter 
and the greater the length, the more resistance is op¬ 
posed to the escape of the current. As in this case the 
resistance is almost entirely a question of surface, the 
best insulator is that having the smallest diameter and 
the greatest length between the wire and the support. 
The latter is accomplished by making the insulator of 
a cup form, or still better, of two cups, one placed 
within the other. 

91. The material of which the insulator is composed 
should be a poor conductor of electricity and heat, a 
non-absorbent of moisture, with a surface repellant of 
water, and free from pores or cracks. It should also 
remain unaffected by exposure to the weather, and the 
effects of heat and cold. Nearly all of the materials 



INSULATION. 59 

ordinarily employed are, however, liable to some of 
these objections. 

Insulators of glass and porcelain being conductors 
of heat, a change of temperature from cold to warm 
causes a condensation of moisture upon their surfaces, 

including the portion protect¬ 
ed from the direct action of 
rain, and from this arises 
the principal objection to 
the use of these substances 
in the construction of an in¬ 
sulator. 

Hard rubber is in itself a 
better insulator than glass ; 
but its surface, from exposure 
to atmospheric influences, soon 
loses its property of repelling 
moisture, and becomes rough 
and porous. 

A surface which repels wa¬ 
tery accumulations will cause 
them to flow disconnectedly 
in drops, instead of forming 
a continuous conducting film. 
This property is therefore one 
of great value for the pur¬ 
poses under consideration. 

92. The Glass Insulator. —The insulator most com¬ 
monly employed in this country is the glass. This is 
generally made in the form represented by Fig. 32, 
which is a sectional view of the insulator fixed upon a 
wooden bracket, the latter being securely spiked to the 
side of the pole. The line wire passes alongside the 
groove surrounding the insulator, and is fastened with 
a tie-wire encircling the insulator, both ends of which 
are wrapped around the line wire. The concavity of 
the under side of the glass keeps it dry, in some meas¬ 
ure preventing the current from escaping to the w^t 



Fig. 32. 















60 


MODERN PRACTICE OF THE ELECTRIC TELEtfRAPH. 


bracket and pole through the medium of a continuous 
stream of water. 

93. The Wade Insulator. —This is largely used in 
the Western States. Its construction is shown in Fig. 33. 

A glass insulator, somewhat 
similar in shape to that last 
described, is covered with a 
1 wooden shield, to prevent frac- 
w ture from stones and other 

II'“ • 

causes, the wood being thor¬ 
oughly saturated with hot coal 
tar, to preserve it from decay. 
The line wire is tied to the 
outside of the shield, in the 
same manner as when the glass 
insulator is used. 

This insulator is usually 
mounted upon an oak bracket, 
as in Fig. 33, secured by spikes 
to the side of the pole or other 


support. When it is intended 
to be mounted upon a hori¬ 
zontal cross-arm it is placed 
upon a straight wooden pin, 
instead of a bracket. The pin 
or bracket is usually saturated 
with hot coal tar, in the same 



Fig. 33. 


manner as the insulator shield. 


Fig. 34. Fig. 35. 

94. Farmer’s Hard Rubber Insulator. —This is 
shown in Fig. 34. It is a good insulator when new, 














































































INSULATION. 


61 


but by exposure to the weather its surface becomes 
rough and spongy, and retentive of moisture. It is 
screwed to the under side of the cross-arm or wooden 
block, which is secured to the pole. The best form is 
that which is made with a drip or shed, as shown in 
the figure. If exposed to the direct action of rain it 
ought always to be placed in a perpendicular position. 
It will be noticed that this insulator holds the line wire 
by suspension. 

95. The Lefferts Ixsulator. —This is composed of a 
suspension hook fixed in a socket of glass, of the form 
represented in Fig. 35. This is inserted into a hole 
bored in the under side of a block or cross-arm, and 
fastened with a wooden pin. In painting the arm or 
blocks the paint must not be allowed to get on the sur¬ 
face of the glass. 



96. The Brooks Insulator. —Figs. 36 and 37 show 
the construction of this insulator, which consists of a 
suspension hook cemented into an inverted blown glass 
bottle, which is again cemented into a cast iron shell, 
provided with an arm which screws into the pole, as in 
Fig. 36. Another form is made, designed for attachment 



































































































































62 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


to a cross-arm, as in Fig. 38. The remarkable insula¬ 
ting properties of this arrangement are mostly due to 
the use of paraffine, with which the cementing material 
(sulphur) is saturated. It has also been discovered that 
blown glass possesses extraordinary properties of repel¬ 
ling moisture. Additional advantage of this fact has 
been taken in the construction of this insulator, as may 
be seen by reference to the cut. 

97. Some important improvements have quite recently 
been made in the mechanical construction of the Brooks 

insulator, which are shown 
in Fig. 39. In the old 
form of hook, shown in 
Fig. 37, the wire has three 
bearings. To hold the 
wire securely, it is neces¬ 
sary that these bearings 
should be so direct as to 
make it difficult to place 
the wire in it, and the 
latter is often weakened 
by being bent. The new 
hook, shown in Fig. 39, 
has five bearings for the 
ware, but not so direct as 
Fig. 39. to injure or weaken it by 

bending. The wire can be 
placed m this hook without labor or difficulty, and a 
strain cannot be applied in any direction by means of 
which the wire can be removed or released. 

98. Mode of Testing Insulators. —The proper way 
to test the comparative value of insulators is to fix 
them upon frames or standards, in sets of ten or more, 
and place them where they will be fully exposed to 
the weather. The tests should be made when the 
weather is very wet, by means of a wire attached to 
all of them in the usual manner, and leading to the 
testing instrument, battery and ground. By this means 
the relative resistances of either of the insulators above 
described, and their consequent value in the construc¬ 
tion of a line, may be readily ascertained. 


























INSULATION. 


63 


99. Escape. —When the insulation is defective, or the 
wire comes in contact with the branches of trees, a wet 
wall, or other partial conductor, a portion of the cur¬ 
rent passes to the ground, forming what is technically 
known as an escape. 

100. Weather Cross. —The escape of the current 
from one wire to another one upon the same poles, 
owing to defective insulation, is sometimes wrongly 
called “induction,” or “sympathetic currents.” Wea¬ 
ther cross is a much more appropriate term. 

As electric currents always move in the direction of 
the least resistance, their tendency is to escape from a 
long circuit to a shorter one. This mixing of the cur¬ 
rents from different wires is a much more serious evil 
than a simple escape to ground, for the latter may in 
most cases be overcome by increased battery power ; 
but when cross connection exists between different 
wires upon the same poles, an increase of battery upon 
one wire gives it an advantage over the others, but 
necessarily at their expense. 

The effects of weather crosses usually manifest 
themselves upon the occurrence of a shower sooner 
than the escape to ground, because the horizontal arms 
become wet sooner than the vertical pole. 

On the English lines this difficulty is obviated by 
means of an earth wire attached to each pole, and wrap¬ 
ped around the center of the arms, thus cutting off the 
currents passing from wire to wire, and conveying them 
to the ground. The battery can then be increased at 
will on one wire, without interference with the others. 
A much more economical and effective method of obtain¬ 
ing this result is that of improving the insulation. 

101. Effect of Escapes and Grounds upon the 
Circuit. —If the wire touches a conductor communica¬ 
ting with the earth, or the earth itself, in a moist or 
wet place, so that the point of contact offers little or no 
resistance compared with the wire beyond, the fault is 
called a ground. The effect of a ground or escape is to 
increase the strength of the current going out to the 




64 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


line, and to exhaust the batteries more rapidly. There¬ 
fore, in working with a continuous current, as is the 
case on American lines, the line current increases in 
strength in wet weather, but the variation or difference 
in the current at one station, when the line is opened 
and closed at another, decreases , and the effective sig¬ 
nals are therefore weakened. 

102. Tub Laws of the Electric Current. —The 
laws which govern the propagation and distribution of 
electric currents are so simple, and at the same time so 
important, that every telegrapher should be familiar 
with them. By their aid the phenomena above referred 
to maybe readily comprehended. The most important 
of these laws was first enunciated bv Ohm, in 1827, 
and is known as Ohm's law. It may be briefly stated 
as follows : 

Call the sum of the electro-motive forces.. .E 
“ “ internal resistance of the battery..R 

“ “ resistance of line and instruments. .L 

“ “ the effective strength of current.. .C 

# 

Then C = _ 

It + L 


That is: The effective strength of the electric current in 
any given circuit is equal to the sum of the electro-motive 
forces divided by the sum of the resistances (174). 

103. Practical Application of Ohm’s Law.—First 
Case. —To illustrate the application of this law to cir¬ 
cumstances occurring in practical telegraphy, take the 


E I 

i i|i|i)i :l oo 

5 10 



100 


l' E 

inn 

5 


B 


-ocH 

10 


do 


Flu. 40. 


case of an ordinary telegraph line (Fig. 40), extend¬ 
ing from A to B, and perfectly insulated, having a re¬ 
sistance of 100 Ohms. Let the main batteries, E and 
E' have each an electro-motive force of 1,000, and a 






















INSULATION. 


65 


resistance of 5 ohms, and let the resistance of the in¬ 
struments I and I' be equal to 10 ohms each. The 
total resistance of such a circuit will be : 

100 ohms, line, 1 — T 

20 “ instruments, f 

10 “ batteries, = H 

130 ;l = E + L 

The line being perfectly insulated, the whole cur¬ 
rent from the batteries will necessarily act upon both 
instruments. 

As the effective strength of the current in any cir¬ 
cuit is, by Ohm’s law, equal to AA in this case it will 
be 

2000 


With key open at A or B. = 00.0 

Difference, or effective working strength. = 13.4 


If, on the above line, an escape occurs between the 
stations A and B, offering a resistance of 50 ohms, the 
effect will be the same as if a wire having a resistance 
of 50 ohms were connected from the centre of the line 
to the ground. The current from each battery has a 
tendency to divide at the fault between the two routes 
open to it, in proportion to their relative conductivity; 
or, what is the same thing, in inverse ratio to their 
respective resistances. But in this case the electro¬ 
motive forces and the resistances are exactly the same 
on each side of the fault; and the positive current from 
one battery, and the negative from the other, have an 
equal tendency to escape to ground at the fault. These 
opposite tendencies consequently neutralize each other, 
and no effect whatever is produced upon the circuit by 
the fault as long as the line remains closed both at A 
and B. 

If, however, A is sending to B, his key is alternately 
open and closed. When open, the circuit of the bat- 

5 






GG 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


tery E (Fig. 41) is entirely broken. There will still, 
however, be a circuit from the battery E', through I' 
and the line to the fault F, and thence to the ground. 


i 

HOO- 

10 


50 


50 


• 50 


B. 


Fig. 41. 



By Ohm’s law we find the strength of this current to 
be as follows: 

5 ohms resistance of battery, . . = H 


10 

U it 

“ instrument, 

50 

it it 

“ i hne, 

50 

a tt 

“ fault, 

115 : 

= n 4 - l. 



n _ E 

1000 


c 

1 

+ 

L 115 


With the key closed at A, the strength of the current 
in the instrument at B was found to be 

15.4 

With key open at A, as above. 8.7 

Difference, or effective working force... 6.7 


In this case the latter will obviously be the same, 
wither A sends to B or B to A. 

104. Second Case. —Suppose the same fault to be 
located near A (see Fig. 42). 

The current from the battery E will divide at F, part 
going to the ground through the fault, and the remain- 


r Hti ; m-oo4- 

5 io : 

r 

!50 

100 

■ — 1 oo—[8 Q|I 11- 

10 5 

[cl 1 




Fig. 42. 


der over the line to B, and through the instrument and 
battery4o ground. The current from E' will divide in 





































INSULATION. 


67 


the same manner between the fault and the route 
through I and E. Taking the battery E alone, and 
considering the other battery E' simply as a conductor, 
the two circuits beyond the fault give the following 
resistance : 


1. By the line instrument and battery at B.. 115 ohms. 

2. “ fault F. 50 “ 

115 x 50 

Their joint resistance will be *. ^ 15 ^ ^ ~ 5U ~ 34.8 ohms. 


Add resistance of battery itself, 5 ohms, and instru 


ment, I, 10 ohms. 15 

The total resistance will be. 49.8 


1000 

And the current leaving the battery, E, = = 20 


This current will divide at the fault between the two 
circuits, whose resistances are respectively 115 and 50, 
or in the proportion of 23 to 10. Therefore 23 parts 
of the current will go to the ground at F, and 10 parts, 
= 20 = 6.1, will go over the line to B. 

The current from the other battery, E', in like man¬ 
ner divides at F, between the fault and the circuit 
through the instrument and battery at A. The joint 
resistance of the two circuits is 

15 x 50 


Add the resistance of the battery E, 5 ohms, instrument I, 10 

ohms, and line, 100 ohms. 115.0 


Total resistance. 

The current leaving the battery E will therefore be 


1000 

120.5 = 


126.5 

7.9 


The resistance of the two circuits beyond the fault 
being 15 and 50, or as 3 to 10, 3 parts will go to 

ground and 10 parts, or —^ = 6.1, through I. 


* The joint resistance of any two circuits is found by dividing the product of the 
two resistances by their sum. When there are three circuits, first find the joint re¬ 
sistance of two circuits as above, and treat it as a single circuit, again applying the 
same rule. In the same manner the joint resistance of any number of circuits may 
be calculated (175). 




















68 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


When A sends to B, the current in the instrument 
at B will be : 

Key closed at A. 

From battery E'. *7-9 

“ “ * E. 6.1 


Total strength in I'. 
Key open at A. 

From battery E'... 

E ... 


14.0 


1000 

165 


6.1 


u u 


0.0 6 1 


Difference, or available working current at B, 


7.9 


Now let B send to A. The current at A will be : 

Key closed at B. 

From battery E. 20.0 

“ “ E'. 6.1 


Total strength in I. 
Key open at B. 

From battery E ... 
“ “ E'.., 

Total strength in I. 


26.1 


1000 

65 


= 15.4 


0.0 


Difference, or available working current at A, 

, E 1 r 

l|l 11-00- 

10 10 

50 


0. 


100 


15.4 

10.7 


l 

-ocH 

10 


E' B 

lli|l|K 

5 


El 


Fig. 43. 

105. Third Case. —Let the battery at A be doubled, 
the fault remaining as in the last case. The electro¬ 
motive force and internal resistance of E are both dou¬ 
bled, as in Fig. 43. The current from E will now be : 

2000 


20 + 


50 x 115 = 36.5 


50 + 115 

which will divide at the fault in the same proportion 
as before, the part going to B being - 3fi ^ 10 = 11.0. 

1000 

The current from E' will be n ? + 2Q * 50 = 7.7, and the 

20+50 

portion reaching A = 5.5. 








































INSULATION. 


69 


When A sends to B the signals will be as follows : 


Key closed at A. 

Current at B = 7.*7 + 11.0 = 18.7 
Key open at A. 

Current at B. 


1000 

165 


= 6.1 


Effective strength at B, 


12.6 


Now let B send to A : 

Key closed at B. 

Current at A = 36.5 -f- 5.5 = 42.0 


Key open at B. 
Current at A, 


2000 

70 


= 28.6 


Effective strength at A. 


13.4 


1 

IIIIHOO- 

5 10 


I E 

-f 


' B 


a 


100 


-OO- 


10 10 


I IB IK 


50 




Fig. 44. 


106. Fourth Case. —Double the battery at B, the 
fault remaining unchanged. See Fig. 44. 


1000 

Current from E = , 50 x 120 

15 +- 

50 + 120 

19.9 x 5 

Portion going to B... = --—- 

2000 

Current from E' = 10A , 50 x 15 

- + 50 4- 15 

15.2 x 10 

Portion going to A.. = -^-- 


19.9 

5.8 

15.2 

11.7 


A sending to B : 

Key closed at A. 

Current at B = 15.2 + 5.8 = 21.0 
Key open at A. 

2000 

Current at B. = = 11.8 


Effective strength at B. 9.2 


































I 


70 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 

B sending to A : 

Key closed at B. 

Current at A = 19.9 + 11.7 = 31.6 
Key open at B. 

1000 

Current at A. — -- = 15.4 

bo _ 

Effective strength at A. 16.2 

107. Thus we find that on a circuit consisting of 

Line wire resistance. 100 ohms. 

2 batteries “ 10 “ 

2 instruments “ 10 “ 

each battery having an electro-motive force of 1000, 
the signals received will be as follows : 

Signals at A. Signals at B. 


When the line is perfect. 15.4 15.4 

With escape 50 ohms in centre. 6.7 6.7 

Same fault at A. 10.7 7.9 

Same fault at A, with battery doubled at A .... 13.4 12.6 

Same fault at A, with batterv doubled atB. 16.2 9.2 


108. The results of this investigation may be sum¬ 
med up as follows : 

When the batteries and instruments are equal at 
each end of a line, a given fault will interfere most 
with the working of the circuit when in the centre. 

When the fault is near one end of the line, the sta¬ 
tion farthest from it will receive the weakest signals, 
and the station nearest it the strongest signals. 

In increasing the battery power for working over an 
escape, the addition should be made to the battery 
nearest the fault. 

109. Distribution op Battery Power. —If the in¬ 
sulation of a line was perfect at all times, the position 
of the battery in the circuit would be a matter of in¬ 
difference. As all lines, however, are subject to more 
or less leakage or escape throughout their entire length, 
the whole battery should not be located at one end of 
a long line, for in this case signals would be received 
much better at one end of the line than the other. The 
usual arrangement is to place half the battery at each 













INSULATION. 


71 


end of the line, although if the escape be uniform 
throughout the entire length of the line, the effect upon 
its working will be the same, whether all the battery 
is placed in the centre of the line or a portion of it in 
the centre and the remainder divided equally between 
the two ends. 

If a certain portion of the line is especially defective 
in its insulation, the distribution of battery power may 
sometimes be varied in accordance with the principles 
laid down, with manifest advantage. 

The insulation of the batteries themselves is a mat¬ 
ter of great importance, and should never be neglected. 
(29.) 

110. Working several Lines from One Battery.— 
It has been for many years the practice in this country 
to work a considerable number of lines at the same 
time from a single battery. The number of wires that 
can be worked in this manner without interference de¬ 
pends entirely upon the proportion between the inter¬ 
nal resistance of the battery employed and the joint 
resistance of all the circuits connected with it. If the 
resistance of the battery itself is inappreciably small 
in comparison with that of the lines connected with it, 
the current on any given circuit will vary but little, 
whether the others be open or closed. With the Grove 
battery of, say, 50 cups, it is possible to work as many 
as 40 or 50 well insulated lines, of 300 miles or more 
in length, without appreciable interference. The great 
objection to this system is that, in wet weather, the re¬ 
sistance of the lines is enormously diminished, and the 
interference of one circuit with another, as a necessary 
consequence, greatly increased. 

It is a common practice when this occurs to increase 
the number of cups in the battery, which in most cases 
has a tendency to aggravate the very evil it is sought 
to remedy; for with every such addition the resistance 
of the battery becomes greater in proportion to that of 
the lines, and the currents more unsteady and fluctu¬ 
ating. No small part of the trouble experienced in 


72 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


working lines in wet weather arises from this cause, 
although usually attributed entirely to defective insu¬ 
lation. It is true, however, that the latter indirectly 
causes the difficulty, by lessening the resistance of the 
wires. 

111. Experiments made on a very wet day, upon a 
number of circuits of nearly the same length (100 miles), 
leading out of New York city, proved that when one 
such wire was attached to a carbon battery of 60 cups 
the addition of three other similar wires reduced the 
current on the first one 12 per cent. It is a common 
practice to attach as many as eight wires to such a bat¬ 
tery, which in the above case would have reduced the 
current about 25 per cent. 

112. It is the opinion of many scientific experts in 
practical telegraphy that increased efficiency, as well as 
economy, would result from working telegraph lines 
with a single series of Daniell’s battery, in its most ap¬ 
proved form, upon each circuit. The objection urged 
against this battery is the increased amount of room it 
takes up, as well as its somewhat greater original cost. 

113. As long as the present system remains in vogue, 
care ought to be taken that the different circuits leading 
from the same battery are as nearly as possible equal 
in resistance; and it must not be forgotten that the in¬ 
terference caused by attaching too many wires to a 
battery cannot be remedied by the addition of more cups 
for intensity. The electro-motive force of a carbon bat¬ 
tery is exhausted with a rapidity nearly in proportion 
to the number of circuits supplied from it. In the case 
of the Grove battery this effect is not so apparent. 


CHAPTER YI. 


TESTING TELEGRAPH LINES. 

' 114. Interruption and interferences from various causes 
are constantly occurring upon telegraph lines, and one 
of the most important of an operator’s duties is to be 
able to discover promptly the nature and location of a 
fault, that measures may immediately be taken for its 
removal. This is done by an investigation called test¬ 
ing. The apparatus and methods now in general use 
in this country are of a somewhat primitive nature, but 
the improved modes of testing which have long been 
employed in Europe are gradually becoming appreci¬ 
ated here, and as these are based on sound scientific 
principles, it is to be hoped that they will soon super¬ 
sede the imperfect ones heretofore employed. 

115. The principal interruptions to which a telegra¬ 
phic circuit are liable may be summed up as follows: 

Disconnection. —The continuity of the circuit is 
broken, so that no current passes over the line. 

Partial Disconnection. —This is usually caused by 
rusty and unsoldered joints in the line, or by loose 
screw connections in offices or about switches, which 
offer great resistance to the passage of the current. 

Escape or leakage of current from the line to the 
ground, caused by defective insulation, or contact with 
trees, &c. When an escape is sufficient to entirely 
prevent the working of the line it is called a “ground” 

Cross. —When two wires are in contact, so that one 
cannot be worked without interfering with the other. 

Weather Cross. —When a portion of the current 
from one wire leaks into others upon the same poles, 
through defective insulation. The effect is similar to 
that of a cross, but much less strongly marked. This 
is often improperly called sympathy , or induction. 







74 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


Defective Ground Connection. —It sometimes hap¬ 
pens that the ground wire, or ground plate, at a termi¬ 
nal station, is defective. The effect of this is to make 
the wires connected with it appear as if in contact, or 
crossed. This difficulty is often caused by the removal 
of a meter in offices where a gas pipe is used as a 
ground connection for several lines. 

116. Testing for Disconnection. —If the circuit is 
broken at any point the relays will all remain open. 
The operator at each way station should immediately 
proceed to test the wire by connecting his ground wire, 
first on one side of the instruments and then on the 
other. If either connection closes the line circuit, the 
interruption is on that side, as the circuit of the oppo¬ 
site main battery is completed through the ground, in 
place of the broken wire. If the ground wire gives no 
circuit either way, it is probable that the interruption 
is in the office, or that the ground connection is defec¬ 
tive. Each operator should always first make sure 
that the fault is notin or about his own office. Having 
ascertained the direction in which the difficulty lies, he 
should at once report the state of the case to the ter¬ 
minal station at the opposite end. 


A B F C D 



□ G __□ Q_!D 


Fig. 45. 

Fig. 45 represents a line with four stations, A, B, C 
and D. Suppose the wire broken at F. By connect¬ 
ing the ground wires at B and C, as shown, two dis¬ 
tinct circuits are formed. A can work with B, and 0 
with D, showing that the fault is between B and C. 

Disconnection is usually caused by the breaking of 
the line wire, or by a key carelessly left open. Some 
other causes are wires loose in their binding screws, or 
defective switches, or the fine wire in or about the re- 














TESTING TELEGRAPH LINES. 75 

lay may be broken. The latter is sometimes burned 
in two by atmospheric electricity. 

117. Partial Disconnection.— It is rather difficult 
to discover this fault by the ordinary relay tests. It is 
frequently of an intermittent character, and requires to 
be very carefully tested for. In the latter case, the 
best plan is to cross connect, or interchange the defec¬ 
tive wire with a good one at the terminal, and also one 
other station, as in Fig. 46. Suppose the fault is at F, on 
No. 2 wire; by cross connecting at A and B, as shown, 



Fig. 46. 


the fault will shift to No. 1 circuit, showing that it is 
between those points. If it were beyond B, it would 
remain on No. 2 circuit. In this case, let the wires be 
put straight at B, and cross connected at C, and so on, 
station by station. When the fault is passed it shifts to 
the other circuit, and will therefore be found between 
tile two last stations. 

118. To Test for an Escape. —Call the stations up 
in rotation, beginning with the one farthest off, and 
have them open key for a minute or two. When a 
station beyond the escape is open, more or less current 
will still pass out to the line through the relay, return¬ 
ing through the ground from the fault. 



Fig. 47. 


Suppose A (Fig. 47) is testing. When the circuit is 
open at C or D a current will pass from E through the 
fault, F, which will be interrupted when B opens, show¬ 
ing the fault is between B and C. 
















76 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


119. Testing for Grounds. —A ground is tested 
for in a similar manner. The operator at a way sta¬ 
tion can ascertain which side of him the ground is 
situated, from the fact that it cuts off or greatly weak¬ 
ens the main battery current from that direction, when 
tested with a ground wire by means of the finger or 
tongue. 

Telegraph lines are very liable to be grounded by 
the action of atmospheric electricity upon the lightning 
arresters. These should be carefully looked after at 
frequent intervals, especially where exposed to damp¬ 
ness, as in cable boxes. 

120. Testing for Crosses. —In case a cross is sus¬ 
pected between two wires, say Nos. 1 and 2, instruct 
the most distant station to open one wire, preferably 
the through wire, or No. 1, and “send dots” upon the 
other. Open No. 2 at your own station, and if the dots 
sent on No. 2 at the distant station are received on 
No. 1, the wires are crossed. Care must, of course, be 
taken not to be deceived by the leakage from one wire 
to another, caused by defective insulation. If the 
wires are in actual contact, the signals received upon 
No. 2 wire will be nearly or quite as strong as if re¬ 
ceived upon No. 1. 

Next, instruct the distant station to leave No. 1 open, 
and open it also at your own station. No. 2 will now 
be free from interference, and the stations upon it may 
be signalled without difficulty. Call them in regular 
succession, commencing at the farthest end oi the line, 
and instruct each one in turn to send dots on No. 2. If 
the dots are received on both wires the cross is be¬ 
tween you and the station sending; but if upon No. 2 
only, it is beyond that station. It is better that each 
operator, while sending dots, should open the other 
wire, if practicable. 

The principle of this test will be understood by refer¬ 
ence to Figs. 48 and 49, which represent a two wire 
line, with four stations, A, B, C and D, the wires being 
“ crossed” between B and C. The operator testing for 


TESTING TELEGRAPH LINES. 


77 


the cross is supposed to be at A. In Fig. 48 station C 
has No. 1 open, and station A has No. 2 open. If C 
sends dots on No, 2 the circuit will shift to No. 1, at 
the cross, as shown by the arrows, and the dots will 



a 


Fig. 48. 


come on No. 1 instrument at A, showing that the cross 
is between A and C. In case C were unable to open 
No. 1 the effect would evidently be the same, provided 
it remains open at D. 

Now let C close both wires, and B open No. 1, and 
write dots on 2 (Fig. 49). If No. 2 be open at A, B 
will be unable to work in this case, as both wires are 
open, one at A and the other at B. With both wires 



Fig. 49. 


closed at A, B’s dots will come on No. 2, the current 
from F passing over both wires to the cross, and from 
thence on No. 2, No. 1 being open, as shown in the 
figure. Thus the fault is located between B and C. 

In large offices,' where there are a considerable num¬ 
ber of wires, it will often be found a much more con¬ 
venient and expeditious method of testing for crosses 
for the operator to station himself at the switch with a 
single instrument, which can be placed at pleasure on 
any wire, for the purpose of communicating with differ¬ 
ent stations. When any station is “ sending dots ” the 
testing operator can feel them by placing a finger upon 
the ground wire, and another upon the proper line wire 












































78 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


at the switch. The principle involved is of course the 
same as in the method first described. In wet weather, 
however, testing by the sense of feeling is attended 
with much uncertainty, as it is impossible to distinguish 
between the effect of a metallic cross, or actual contact, 
and the leakage arising from bad insulation. 

121. It would be difficult to specify all the minor in¬ 
terruptions that are liable to occur in and about tele¬ 
graph offices, or on the lines ; the operator will there¬ 
fore, in many cases, be obliged to depend upon his own 
ingenuity for the best method of testing applicable to 
each particular case. By carefully studying, however, 
the principles heretofore explained, the intelligent tele¬ 
grapher will usually be able to cope with any difficulty 
that may chance to arise in the ordinary service of the 
lines. 

122. Testing with tiie Galvanometer and Re¬ 
sistance Coils. —In the more accurate and scientific 
modes of testing, which have been for some years em¬ 



ployed upon the European lines, the instruments used 
are the differential galvanometer and a set of standard 
resistance coils (44). 

The arrangement of the connections will be under¬ 
stood by reference to Fig. 50. 

























TESTING TELEGRAPH LINES. 


79 


The galvanometer coils are wound with two wires of 
the same length and resistance, insulated from each 
other with the utmost care. The needle is, therefore, 
surrounded by an equal number of convolutions of each 
wire, which are also equi-distant from it. 

The inner end of one coil surrounding the galvano¬ 
meter, g , is joined to the outer end of the other at a, 
and a key, K, attached to this junction, when de¬ 
pressed, forms the connection with the testing battery, 
E. The other ends of the coils run to binding screws, 
M M, for the convenient attachment of lines to be 
tested. The principle upon which the action of the 
instrument depends is the following: 

When the battery is connected by depressing the 
key the current divides into two equal portions at a , 
one flowing from a to M, tending to deflect the needle 
to the left, and the other from a to M', tending to de¬ 
flect it to the right; but as long as the two currents are 
of the same strength they balance each other, and the 
needle remains at rest. Suppose that the terminal M' 
is connected to a telegraph line whose remote end is to 
ground, and the terminal M is connected through the 
resistance coils, R, to the ground likewise, as shown in 
Fig. 50. We have already seen (102) that the strength 
of an electric current is in all cases equal to the electro¬ 
motive force divided by the resistance. Therefore, if 
in this case we let 

E = electro-motive force of battery, 
l = resistance of line wire, 
g = resistance of galvanometer coil, 
r = resistance coils in circuit, 

the current in the two circuits surrounding the needle 
will be 

E E 


If, therefore, the resistance coils in circuit be varied 
until r — l, the needle will remain unaffected. As the 
earth offers no appreciable resistance to the passage of 
the current, the resistance of the line l will be accu- 




80 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


rately represented by the amount of resistance inter¬ 
posed at r, in order to bring,the needle to zero. The 
value of the above equation will obviously not be 
affected by any change in the value of E. 

123. The resistance coils, R, accompanying the gal¬ 

vanometer, are so arranged as to be adjustable to any 
required resistance, from 1 ohm up to 10,000. For 
the measurement of still higher resistances one coil of 
the galvanometer is provided with three “ shunts, 77 or 
branch circuits, x , y, z, having resistances respectively 
equal to and therefore, if x be connected, 

to of the current will pass through y, and to through 
the shunt. In the same manner y and z respectively 
allow but tw and toVo of the current to pass through 
one wire of the galvanometer, when connected, and by 
this means the instrument may be made to measure 
any resistance, from 0.001 up to 10,000,000 ohms. 

124. Testing for the Distance of Faults. —The 
principle upon which the methods of distance testing are 
founded is that of finding the resistance of the line wire 
between the testing station and the fault by means of 
the apparatus described. When the line is broken at 
any point one of the following four cases generally 
occurs : 

1. Line wire broken, giving full, or nearly full, 
ground connection. 

2. Line wire unbroken, but gives nearly enough 
escape to ground to make signals imperceptible. 

3. Line wire broken, without making contact with 
earth. 

4. A cross between two wires, so that signals sent 
on one are communicated to both. 

125. It is very essential that the resistance of each 
circuit should be frequently measured and recorded, so 
that when a fault occurs the actual resistance per mile 
of the line may be known. If the broken line gives a 
full ground, its resistance divided by the resistance per 
mile at once gives the distance of the break from the 
testing station ; and if the distant station obtains a 


TESTING TELEGRAPH LINES. 


81 


corresponding result, the confirmation is complete. 
Thus, in a line of 100 miles in length, if the tests from 
the two extremities indicate distances of 45 and 55 
miles, respectively, the locality of the interruption is 
clearly indicated. As the fault, however, usually gives 
a very considerable resistance at the point where the 
line is in contact with the earth, and the sum of the 
two resistances, measured from stations at the opposite 
ends of the line, greatly exceeds the resistance of the 
line itself when perfect, it is usual in such cases to 
estimate the fault midway between the two points indi¬ 
cated. Thus, when the respective resistances indicate 
86 and 26 miles, the sum of these exceeds 100 miles bv 
12, and therefore half this excess, or 6, is deducted 
from each of the measures. 

126. When the line is unbroken, but shows a heavy 
escape or partial ground, sufficient to weaken signals, 
two or three different methods are available for deter¬ 
mining its locality. The first plan is that of direct 
measurement, alternately from each end, the distant 
end at the same time being insulated, or, in other 
words, left open, in the manner explained in the last 
paragraph. In this case the resistance of the fault is 
measured twice over, and is roughly allowed for by the 
method of calculation above given. 

127. The Loop Test. —A second and more accurate 
method, which gives a measure entirely independent of 
the resistance of the fault itself, is known as the loop 
test. It is only available, however, in cases where 
there are two or more parallel wires on the same route. 
In order to make this test, let the operator proceed as 
follows : 

Make the length to be tested as short as possible, 
and have all the instruments in circuit taken out. Se¬ 
lect a good wire, similar, if possible, to the one it is 
required to test. Both these wires must then be con¬ 
nected together in a loop, at the nearest available sta¬ 
tion beyond the fault, without ground connection. The 

resistance of the faulty wire, when perfect, must be 

6 


82 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


ascertained. This may be taken from previous records, 
or it may be found thus : 



Connect one end of the loop to the + pole of the 
battery E, and the other to one of the galvanometer 
wires at M'. Connect also the + pole of the battery 
with the resistance coils, R, at N, and the — pole of 
the battery to the key, K, and common terminal, a, of 
the galvanometer. Connect the remaining galvanome¬ 
ter wire with the resistance coils at M (Fig. 51). 



Having ascertained the resistance of the loop, ar¬ 
range the connections as shown in Fig. 52. 

Upon depressing the key, Iv, the battery current will 













































TESTING TELEGRAPH LINES. 


83 


flow through. M ancl R, and also through the loop. The 
resistance required at R to balance the needle will be 
equal to the sum of the resistance of the two lines. 
Although there is a partial ground at F it will not 
affect the measurement, as there is no other ground in 
circuit. 

Connect the + pole of the battery E to ground, and 
connect the — pole to the keyK. Connect the perfect 
wire of the loop to one of the galvanometer wires at M', 
and the faulty wire to (he other galvanometer wire at 
M, interposing the resistance coils R. When the key 
K is depressed the current from the battery E flows 
into both lines simultaneously, passing to the ground 
through the fault at F. By adding resistance at R, so 
as to bring the needle to zero, the resistance aNF 
will be made equal to a M' F. 

The resistance thus added, deducted from the total 
resistance of the loop, previously ascertained, and di¬ 
vided by two, is the resistance of the line between N 
and F. 

Thus, if the resistance of the loop be 1,000 ohms, 
and 100 ohms have been added to the defective wire to 
balance the needle— 

Then 1000 ~ 10 - ° = 450 ohms, the resistance of the wire 
between the resistance coils R and the fault. 

Let M'P = i6,NP = y. 

Then x + y = L, the resistance of the loop. 

As 11 + y = x, or It 4- N F = M' F. 

L —It 

Therefore, y = —-— 

Suppose that, the loop of 1,000 ohms measures 120 
miles, then, by proportion, 

If 1,000 ohms = 120 miles, 450 ohms = 54 miles. 

When an instrument or section of small wire is in¬ 
cluded in the circuit, allowance must be made for their 
resistance. It is a great assistance in these tests to 
know from previous records the exact resistance of 
every section of the line. 




34 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 

128. Blavier’s Formula for Locating an Escape.— 
Where there is but one wire the following method may 
be employed. Three tests have to be taken for the 
operation, viz: 

Let R = resistance of tho lino before it was defective. This must 
be obtained from previous records. 

“ S = resistance of the line when grounded at the distant end. 

“ T = resistance of tho lino when disconnected at the distant end. 

Multiply S by S and T by R, and add the products 
together; subtract from this amount T times S, and 
also R times S. Subtract the square root of the re¬ 
mainder from S ; the remainder will give the resistance, 
x, or the distance of the fault from the testing station. 

Th is process appears complicated, but is in reality 
very simple. For example, suppose the line 100 units 
long, and the fault 68 units distant, and the resistance 


100 

92 

IGA 

resistances 
We there- 


And the square root of 576 is 24; which deducted, S = 
92, gives 68 as the resistance of a?, or the distance of 
the fault from the testing station. 

The distance, x, being known, the others are obtained 
with ease; for R — 68 gives y, the distance from the 
opposite end; and T — 68 gives z, or the resistance of 
the fault itself. This test should be taken from both 


of the fault 96 units, as shown in Fig. 53 

X68 y32 


Zog~ 


Fiq. 53. 


Then R 
*S 
T 


= x + 


x + y 
v x z 


y + 

X + z 


68 + 32 
32 x 96 
68 + 32 + 96 
68 + 96 


We shall, however, have obtained these 
by measurement, and not by calculation, 
fore have : 


S x S 
T x R 

T x S 
R x S 


92 x 92 
164 x 100 

164 x 92 
100 x 92 


8464 

16400 

15088 

9200 


24864 


l 242 
) “ 5 


24288 
576 


* Seo note, § 104. 






TESTING TELEGRAPH LINES. 


85 


ends of the line, if possible. In the above calculation 
the resistance of the fault is supposed to remain con¬ 
stant during the measurements ; but as this is not often 
the case in practice, the average of several measure¬ 
ments should be taken. 

129. To Find the Distance of a Cross. —The two 
wires in contact form a loop , provided they are clean, 
and are twisted together, so that the contact offers no 
appreciable resistance. In such a case open both wires 
at the nearest station beyond, and test the resistance of 
the loop. Half this resistance will be the resistance of 
the wire between the galvanometer and the fault, and 
from this the distance can be calculated, as before ex¬ 
plained (127). All relays in circuit must be taken out, 
or the proper allowance made for their resistance. 

As it is difficult to tell with certainty whether the 
cross offers resistance or not, it is a better plan to test 
it as a ground. Test each wire in turn by the loop 
method (127), grounding the wire at both ends. The 
wire tested will then make a ground through the other 
wire at the point of contact, and the location of the 
latter may be readily ascertained. 

Second Method *—Suppose two wires, A and B, 
touch one another at the point F. Connect A to the 
zinc of the testing battery, leaving it open at the re¬ 
mote end ; it will then serve as a battery wire between 
the battery and the fault (F). Ground B at the distant 
end, and connect it to one coil of the differential gal¬ 
vanometer at the testing station Put the other wire 
of the galvanometer to ground. The current of the 
battery will pass along the wire A and divide at F, 
one portion going to ground at the distant end of B, 
and reaching the galvanometer through the wire con¬ 
nected with the ground, the other portion returning to 
the galvanometer through the nearer portion of B. If 
the cross is exactly in the centre of B the needle will 
not move, as the two currents will balance each other. 
If one section of B is longer than the other, the resist- 


* Culley’s Handbook, 3d edition, page 279. 





‘30 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 

ance added to the shorter section to balance the needle 
will show the difference in the resistance of the two 
sections. 

Let L = the total resistance of B. 

“ x = resistance of the shorter portion. 
li L — x — “ “ longer “ 

‘ R = resistance added to shorter portion. 

L — R 
Then x = —^— 

130. Advantages of Testing by Measurement.— 
The testing of lines by actual measurement lies at the 
very foundation of all efforts to improve the working 
of our telegraphic system. The insulation resistance of 
each of the principal circuits should be measured every 
morning, and a record of the results kept for reference. 
In England the standard of insulation is 1,000,000 ohms 
per mile in the worst of weather. Therefore, a line 
of 200 miles should not give less than h 3 no ° — 5,000 
ohms. If it gives less than this the low resistance is 
due to defective insulation. The line should, in that 
case, be tested in many separate sections, either from 
the terminal office or by a visit to each section. If the 
resistance per mile is the same for each section, the 
fault is probably owing to the nature of the insulation; 
but if, as is usually the case, some sections are very 
much worse than others, the trouble will be found in 
contact with trees, broken insulators, and the like. A 
visit to the faulty locality will disclose the cause of the 
evil. 

131. In comparing the insulation of line wires of 
different lengths, the insulation per mile must be ascer¬ 
tained, otherwise the longest wire will appear the 
worst; therefore, multiply the insulation test in ohms 
by the length of the wire in miles. If the insulation is 
uniformly good throughout the circuit tested, the leak¬ 
age will increase in direct proportion to the length of 
the wire, irrespective of its thickness or conducting 
power, for the resistance of the wire is very small in 
comparison with the insulators, and need not be taken 
into account. 




TESTING TELEGRAPH LINES. 


87 


The following example from Culley’s work will illus¬ 
trate this. The figures given are the results of an ac¬ 
tual test: 


The wire A had a leakago equal to. 29 

*• B “ “ “ . 30 

“ C “ “ “ . 50 

Total leakage. 109 


The three wires, when connected together at the test¬ 
ing end and left open at the distant end, gave a com¬ 
bined leakage of 110. 

When connected so as to form a continuous wire, open 
at the distant end, the leakage was still 110. The ex¬ 
periment was repeated, and extended to other wires, 
with the same result. In this case the resistance of the 
insulators was very great compared with that of the 
wire—as much as two million ohms per mile. But on 
a wet day three similar wires, whose respective leak¬ 
ages were 196, 185 and 141, making a total of 552, 
when looped in a continuous line, as in the second case 
above, gave a test of only 476, the distant portion of 
the wire being in reality tested by a current weakened 
by the leakage in the nearer portions. 

132. Testing for Conductivity Resistance.— The 
metallic resistance of the line wires should be occasion¬ 
ally tested in sections, in the finest weather. The re¬ 
sistance should be uniformly in proportion to the length 
of the wire. If any section discloses an unusually high 
resistance per mile, it is very probable that there are 
rusty, unsoldered joints in the line, or that the ground 
connections are defective. It is difficult for those who 
have not tried it to believe the vast improvement that 
may be made in any line in a few days by actual mea¬ 
surement, and an inspection of the sections which give 
indications of being defective. 

It is not an uncommon occurrence to find that a single 
unsoldered joint in galvanized iron wire, which appears 
perfectly firm and sound, will give a resistance, when 
tested by the galvanometer, equal to many miles of 
line. A line containing many bad joints wiU frequently 







88 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


work better in wet than in dry weather, as the mois¬ 
ture increases the conductivity of the oxide between 
the wires at the joints. 

In testing for conductivity, with the distant end of 
the wire to ground, as in Fig. 54, the result is some¬ 
times interfered with by earth currents . It is there¬ 
fore better, when practicable, to use the loop method, 
by connecting the wire to be measured in a loop with 
another wire of known resistance. Unless this test is 
made in fine weather, however, the leakage from one 
wire to the other will decrease the resistance of the 
loop. The battery must also be insulated from the 



earth, otherwise the leakage at each insulator will de¬ 
crease the apparent resistance, especially if the insula¬ 
tion is defective. For instance, two wires on the same 
poles, disconnected and looped at the distant end, had 
a resistance of 6,475 ohms when the battery was en¬ 
tirely disconnected from the earth. Upon putting the 
zinc pole of the battery and the line attached to it to 
earth, the apparent resistance fell to 5,250 ohms. The 
insulation resistance, with one wire disconnected, was 
9,250 ohms, the weather being damp. 


























CHAPTER VII. 


NOTES ON TELEGRAPHIC CONSTRUCTION. 

133. In order to maintain uninterrupted telegraphic 
communication between any two points, it is of the first 
importance that the line should be well constructed and 
properly insulated throughout. There are numerous 
minor details in the construction and repairing of tele¬ 
graph lines which merit much more attention than they 
generally receive. The bad working of our lines is in 
a great measure owing to the neglect of these appa¬ 
rently trifling details, through ignorance or carelessness. 

134. Poles. —The poles intended for an ordinary 
line should never be less than five inches in diameter 
at the top, their length depending upon the number of 
wires to be provided for, and in some measure upon 
the location of the line. They should be set in the 
ground to the depth of five feet, wherever practicable. 

In setting poles around the curve of a railway, they 
should be made to lean back against the strain of the 
curve. 

135. Wire. —For ordinary lines, galvanized iron 
wire, of No. 8 or 9, Birmingham gauge, is generally 
employed. For short lines, No. 10 or 11 will answer 
very well. The “American Compound Wire,” a re¬ 
cent invention, is composed of a combination of a steel 
core with a sheathing of copper. It has come into ex¬ 
tensive use within the short time which has elapsed 
since its introduction, and has, thus far, been found to 
answer admirably. A wire of this kind, having a con¬ 
ductivity equal to a No. 8 iron wire, weighs but 112 
pounds per mile. 

136. The less the size, and consequently the conduc¬ 
tivity of the line wire, the more care is required in its 




90 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


insulation, for an increased resistance virtually adds to 
the length of the circuit. Increased conductivity thus ad¬ 
mits of a reduction in battery power, with a consequent 
decrease in the escape of electricity, and long circuits 
may be thus worked with much greater facility; a fact 
which has been most unaccountably ignored in the con¬ 
struction of the greater portion of the lines in this 
country. 

137. Galvanized or Zinc Coated Wire must 
always be used for permanent work, for rust reduces 
the conducting power of wires very rapidly. This is 
especially the case with the smaller sizes, such as No. 
11 or 12. In smoky places it is a good plan to paint 
the wire before it is put up, for the gas arising from the 
combustion of coal destroys the zinc coating in a short 
time, as may be observed in many of our larger cities. 

138. Arrangement of Wires upon the Pole.— 
Wires arranged vertically upon the poles, or one above 
another, are more liable to get into contact with each 
other than when arranged horizontally upon cross-arms. 
When placed one above another, each alternate wire 
should be fastened upon opposite sides of the poles. 

It is better not to place wires of different sizes upon 
the same poles or cross-arms if it can be avoided, as 
they are much more likely to get “ crossed ” than wires 
of the same size would be, as they do not keep time 
with each other when swung to and fro by the wind. 

139. Joints or Splices. —In the construction of a 
line nothing is of greater importance than the perfect 
continuity of the circuit, and this depends, in a great 
measure, upon the perfection of the joints. The impor¬ 
tance of this has been very generally overlooked by 
the telegraphers of this country, and much trouble in 
working lines has been experienced in consequence, the 
cause of which has remained unsuspected. A single 
rusty unsoldered joint will often cause more resistance 
than fifty miles of line. 

No joint or splice, however clean and firm, can be 
depended upon if made by mere contact or twisting. 



NOTES ON TELEGRAPHIC CONSTRUCTION. 


91 


Sooner or later the metals will certainly rust, and this 
tendency is increased by the passage of the current. 
When copper and iron wires are joined together the 
joint is especially liable to become defective from this 
cause. It is a common error to suppose that joints 
made in galvanized wire do not require soldering. 

140. In making a joint each wire should be twisted 
round the other, in the manner represented in Fig. 55, 
the turns passing as close, and as nearly at right angles 
as possible to the wire which they surround. A wire 
must never be spliced by being bent back and twisted 
around itself. 



Fig. 55. 


141. The best solution for soldering is chloride of 
zinc, with a little muriatic acid added, for the purpose 
of cleansing the wire. In connecting copper and iron 
wire together, it is well to wash off the chloride of zinc, 
and then coat the joint with paint or rosin, or else to 
solder with the rosin alone. This will prevent local 
galvanic action between the metals. 

142. Fixing the Insulators. —In attaching insula¬ 
tors to the poles they should be arranged in such a 
manner as to prevent, as far as possible, the lodgment 
of snow about them, so as to form an escape between 
the wire and its support. The glass insulator is usually 
cemented to the bracket by means of white lead or 
asphaltum. The edge of the insulator must never he per¬ 
mitted to touch the shoulder of the bracket; for in this case, 
during a shower, a continuous stream of water flows 
directly from the wire to the pole, entirely destroying 
the usefulness of the insulator. For the same reason 
an insulator ought.never to be fastened down to a 
bracket by means of a spike driven over it, as is often 
done where there is an upward strain upon the wire. 
The proper way, in such cases, is to use some form of 









92 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


hook, or suspension insulator, and fasten the line into 
it with a tie-wire. 

In turning a sharp angle it is better to put on two 
insulators and brackets at the corner pole, or the wire 
will be liable to come in contact with it. 

When the Lefferts or Brooks insulator is used, there 
is danger of fracturing the glass while stringing wire, 
by violently wrenching the wire into the hooks. By a 
little precaution this result may be avoided. 

143. Insulators and brackets are sometimes attached 
to a cross-arm, or other support, in a horizontal posi¬ 
tion. This ought never to be allowed, for a driving 
rain will wet the whole inner surface of the insulator, 
causing a great leakage of the current at every sup¬ 
port. The same thing often occurs with improperly 
shaped brackets, which cause the spray from falling 
rain-drops to be dashed against the inside of the insu¬ 
lator. The shoulder of the bracket ought to be rounded 
or sloped off, so as to prevent this from happening. 

Unless the insulator is securely fastened to the pin 
or bracket which supports it, it is liable to be lifted off 
by the wind, causing an interruption. 

144. Leading Wires into Offices. —The wires lead¬ 
ing into offices are fruitful sources of escapes and other 
interruptions, as the work is often very unskilfully or 
carelessly done. Gutta-percha covered wires, unless 
well protected, become entirely useless in a year or 
two, if exposed to the air and light. The method em¬ 
ployed in England to protect this kind of wire might 
be adopted with great advantage in this country. The 
gutta-percha wire is first covered with tape, and then 
saturated with a preservative mixture.* 

The best way to lead wires through the side of a 
building is to enclose them in hard rubber tubes, with 


* This mixture is made and applied as follows: Take equal portions of wood tar, 
gas tar and slacked lime. Boil these together, stirring them well while boiling, until 
the moisture is entirely driven out, which may be known by the subsidence of the 
frothing. When cool apply to the taped wire, and then cover the latter with dry 
sand. Hang the wire up to dry in the air, and in three or four days it will be 
ready for use. This coating resists sun and moisture, and effectually protects th© 
gutta-percha. 



NOTES ON TELEGRAPHIC CONSTRUCTION. 


93 


the outer ends inclined downwards, to prevent moisture 
from entering. In arranging these wires, it should be 
borne in mind that the current will follow moisture and 
dampness along the outer surface of covered wire, 
unless it is so placed that the line of leakage is broken 
at some point. 

145. Fitting up Offices. —In running wires inside 
an office, it is better never to allow hvo wires to touch 
each other, even when covered with an insulating coat¬ 
ing, as this may be burned by lightning or otherwise 
rendered imperfect causing a cross-connection. The 
proper mode of arranging the office connections and 
running the wires to the instruments is shown in Figs. 
17 and 18, pages 34 and 35. Splices in the office wires 
should be avoided as far as possible, but when required, 
they should be made by turning each wire eight or ten 
times around the other. A less number of turns 
answers for the line wire, because the strain tends to 
keep the joint pressed together. Great care must be 
observed in making the joint between the iron and cop¬ 
per wire, which must in all cases be soldered. 

146. Ground Connections. —It is of the utmost 
importance that the ground plate at each end of the 
line should make a perfect connection with the earth. 
The plate must be large, and buried deep in wet soil 
below the reach of frost. A water or gas pipe makes 
an excellent ground connection. The ground wire 
should be attached outside the metre, as the latter 
is liable to be occasionally disconnected for repairs. It 
is advisable, whenever practicable, to form a connection 
both with the gas and water pipes. The connection 
should be carefully made and always well soldered. 

147. Cables. —The shore ends of cables should be 
bedded well out to low water mark. Dig the trench 
to a good depth, and cover the cable with a piece of 
heavy plank or joist, and secure it well with heavy 
stones, laid at short intervals. If the covering be 
merely of sand it will soon wash away and leave the 
cable uncovered. Never allow any 'portion of a cable to 




94 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


be exposed to sun or air , but cover it all the way from 
the box where the connection is made with the air line. 

Cable boxes always ought to be made double (one box 
within another), in order to prevent wet from entering. 
The unskilful manner in which these are often arranged 
is a fruitful source of trouble in working lines. 

Lightning arresters should be kept attached to cables 
all the year round . It is not uncommon for heavy light¬ 
ning to occur in midwinter in this country. 

148. Making Joints in Cables. —In splicing cables, 
or other gutta-percha wire, the following is the method 
recommended by the Bishop Gutta-Percha Company, 
who have manufactured the greater portion of the sub¬ 
marine cables in use in this country : 

“Use gutta-percha one sixteenth of an inch thick, cut 
in pieces to suit the joint. Soften it in hot water, and 
keep it flat Wipe the surface with a cloth. Heat the 
surface by holding it near a flat file or other iron, about 
as hot as a laundress’s iron ; if the iron causes the 
gutta-percha to smoke, it is too hot. When dry and a 
little sticky , wind two or three coatings of gutta-percha 
around the joint, taking care that each coating is per¬ 
fect and each layer is dry ; then smooth off and lap 
the joint well over on the gutta-percha on each side of 
the joining. Use no spirit lamp , nor anything with a 
blaze. When gutta-percha is burned it cannot be re¬ 
stored. Hot water joints arc worthless. They will not 
stand, and will open when dried out. 

“In making joints it is absolutely necessary that the 
hands of the operator should be clean, and that no 
water, grease, dirt, or anything of the sort must be 
allowed to touch the gutta-percha.” 

149. Another method is given in Gulley's Handbook 
of Practical Telegraphy t as follows : 

“Prior to making the joint the gutta-percha is 
removed from the ends of the wires for about one and 
a half inches, and the copper wires are carefully cleaned 
by scraping; the wires are twisted together for one 
inch, the sharp ends being closely trimmed off. The 



NOTES ON TELEGRAPHIC CONSTRUCTION. 


95 


joint is then soldered with rosin and good soft solder, 
containing a sufficiency of tin. 

“After this the gutta-percha is scraped, or very 
carefully pared back for about two inches, to remove 
its outer surface, which is oxidized, and will not join 
properly ; the wire joint is covered with Chattcrton’s 
compound* and the gutta-percha, heated on both sides, 
and tapered down over the joint till that from each side 
meets. The junction is completed by means of a warm 
joining tool, care being taken to mix the gutta-percha 
well without burning. As soon as this has cooled an¬ 
other coating of Chatterton’s compound is spread over 
the gutta-percha, taking care not to burn the compound. 

“ A new and clean sheet of gutta-percha is then 
heated by means of a spirit lamp, and while so heated 
carefully stretched so as slightly to thin it. Then, 
while it and the Chatterton coated joint are still hot, it 
is laid on the joint, and pinched tightly round it with 
the finger and thumb, after which it is trimmed off close 
with scissors. The seam is again pinched and carefully 
finished off with a warm tool, so as to mix the gutta¬ 
percha of the two sides, and the coating of the wire 
itself, well together. 

“The joint, when cool, is again covered with Chat¬ 
terton’s compound, and a longer and larger sheet of 
gutta-percha is laid over it, pinched, cut, and tooled off 
as before. 

“When the joint is complete, another coating of 
Chatterton’s compound is applied over the whole, well 
tooled over the joint, and when cool, rubbed with the 
hand, well moistened, till the surface is smooth. 

“The mixing of the old and the new gutta-percha 
is most important, and joints generally fail from this 
having been imperfectly done, or from the percha being 
overheated. Cleanliness is essential to success. The 
fingers should be used as little as possible, and must be 
kept very clean.” 


* The ingredients of this are by weight, as follows* one part of Stockholm tar; 
one part of rosin, and three parts of gutta-percha. 




CHAPTER YI IT. 


HINTS TO LEARNERS. 

150. Formation of the Morse Alphabet. —Th*? 
characters of the American Morse Alphabet are formed 
of three simple elementary signals, called the dot , the 
short dash and the long dash , separated by variable 
intervals or spaces. There are four spaces employed in 
this alphabet, viz., the space ordinarily used to sepa¬ 
rate the elements of a letter; the space employed in 
what are termed the “spaced letters/ 7 which will be 
hereafter referred to ; the space separating the letters of 
a word; and lastly, that separating the words them¬ 
selves. 

The value of these spaces should be carefully im¬ 
pressed upon the mind of the learner. Beginners are 
apt to conceive that the Morse alphabet consists solely 
of dots and dashes, and this misconception has a ten¬ 
dency to greatly increase the time required to become 
good “senders.’ 7 Uniformity and accuracy in spacing 
is of no less importance than in the formation of the 
letters themselves. The foundation of perfect Morse 
sending lies in the accurate division of time into mul¬ 
tiples of some arbitrary unit. 

151. The duration of a dot is the unit of length in 
this alphabet. 

1. The short dash is equal to three dots. 

2. The long dash is equal to six dots. 

3. The ordinary space between the elements of a let¬ 
ter is equal to one dot. 

4. The space employed in the “spaced letters 77 is 
equal to two dots. 

5. The space between the letters of a word is equal 
to three dots. 

6. The space between two words is equal to six dots . 



HINTS TO LEARNERS. 


97 


The dot is an unfortunate appellation for this sign, 
because it conveys the idea of a point, or to speak elec¬ 
trically, a current of infinitely short duration. Elec¬ 
tro-magnets, however, require time in magnetization 
(38). Currents involve time in transmitting signals. 
Clock-work requires time to run. Currents must be ot 
sensible duration. The dot, therefore, involves time , 
but this time is variable, according to circumstances. 
The length of the dot should increase with the length 
of the circuit. In long submarine lines the dot has to 
be made longer than the dash itself on short open air 
lines, and the same thing occurs in working through 
repeaters (76). In commencing, therefore, the habit 
should be acquired of making short, firm dashes , instead 
of light, quick dots. After the student has once learned 
to send well, it is very easy to learn to send fast , but 
after once getting in the habit of sending short and 
rapid dots, or “clipping,” it is almost impossible to 
get in the way of sending firmly and steadily. Begin 
ners should rather take pride in the accuracy with 
which they space out the elements of the telegraphic 
music than in the number of words they can stumble 
through in a minute. 

152. In the excellent little Manual of Prof. Smith* 
six elementary principles are laid down as the basis 
for practicing the alphabet, viz: 

First principle. Dots close together. 

I S H P 6 

mm m m m m m m m m m m m m mm mm m m m *i> 

4 

Second principle. Dashes close together. 

M 5 If 

Third principle. Lone dots. 

E 

Fourth principle. Lone dashes. 

T L or cipher 


** Published by L. G. Tillotson & Co., New York 

7 




98 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


Fifth principle. A clot followed by a dash. 

A 

Sixth principle. A dash followed by a dot. 

N 

153. Correctness in sending depends in a great mea¬ 
sure upon the manner in which the key itself is handled. 
Place the first two lingers upon the top of the button 
of the key, with the thumb partly beneath it, the wrist 
being entirely free from the table. The motion should 
be made by the hand and wrist, the thumb and lingers 
being employed merely to grasp the key. The motion, 
both up and down, must be free but firm. Tapping 
upon the key must be strenuously avoided. 

154. The downward movement of the key produces 
dots and dashes; the upward movement spaces. It is 
first necessary to acquire the habit of making dots with 
regularity and precision, then dashes, and finally com¬ 
binations of dots and dashes. It is the best plan for 
the student to practice upon a register in a local circuit 
with his key, as he will the more readily be able to 
observe and correct the faults in his manipulation. 

155. The student may now proceed to practice upon 
the elementary principles. 

1. Practice making dots at regular intervals, until 
they are produced with the regularity of clock-work, 
and of definite arid uniform dimensions. The regular 
tick of a watch or of a short pendulum is a valuable 
auxiliary in acquiring this habit. 

2. Next proceed to make dashes, first at the rate of 
about one per second of time, which may afterwards be 
slowly increased to three. The space between the 
dashes must be made as short as possible. If the up¬ 
ward motion of the hand, in forming the space, be made 
full, it cannot be made too quick. 

3. The third principle occurs but once in the alpha¬ 
bet, and forms the letter E. It is made by a quick but 
firm downward movement of the key. In practicing 


HINTS TO LEARNERS. 


.99 


upon this or any other character, it should not be 
repeated too rapidly, nor should the thumb and lingers 
be taken from the key in the intervals between the suc¬ 
cessive repetitions of the letter. 

4. The fourth principle is somewhat difficult. The 
usual tendency is to make T too long and L too short. 
It will be observed that the same character is used for 
L and the cipher or 0. Occurring by itself or among 
letters it is always translated as L, but when found 
among figures becomes 0. This would at first seem 
liable to cause confusion, but in practice it is found not 
to be the case. It was formerly the custom to make 
the cipher equal to three short dashes. 

5. The fifth principle, which forms the letter A, may 
be timed by the pronunciation of the word again , 
strongly accenting the second syllable. The tendency 
of beginners is usually to make the dot too long and 
the dash too short, and more especially to separate 
them too much. 

G. The final principle, the dash followed by a dot, 
usually presents some difficulties. The universal ten¬ 
dency of the student is to separate the dot from the 
dash by too great a space. Time the movement by 
pronouncing the word ninety, with the first syllable 
somewhat longer than usual. 

156. Having become thoroughly conversant with the 
six elementary principles, the following exercises may 
be taken up in order. 

(1.) E I S H 

These should be practiced separately, until the right 
number of dots can be made invariably, the last dot in 
each being neither shorter nor longer than the prece¬ 
ding ones. 

(2.) T M 5 % - Lor cipher. 

In practicing this exercise, care must be taken not 
to separate the dashes too much, and to make the final 
one in each letter exactly equal to the preceding ones. 




100 


MODERN PRACTICE OE TIIE ELECTRIC TELEGRAPH. 


Observe not to make the L too short. There is a gen¬ 
eral tendency in beginners to shorten the final dash, 
where two or more occur together. 

(3.) A U V 4 

The usual tendency to make too much space between 
the dot and dash, in the above letters, may be avoided 
by making them as if by prolonging the final dot in 1, 
S, H and P. 

(4.) I A S U 

■i m m mm m m m mm mmm 

H V P 4 

These are to be practiced in couples, as represented, 
the object being to impress upon the student the differ¬ 
ence in the characters thus coupled together. 

(5.) N D B 8 

The student having thoroughly mastered the sixth 
elementary principle, he will have no difficulty in form¬ 
ing the above characters. 

O 

(6.) A F X Parenthesis 

Comma Semicolon W 1 

The only caution necessary in this exercise is to form 
the letters compactly, with the dashes of equal length. 
(See Exercise 2.) Observe, that the Parenthesis may 
be formed by running A U together, and the Semicolon 
by A F, etc. 

(7.) U Q 2 Period 3 

These differ but little from exercises previously prac¬ 
ticed, and require no particular directions. 

(8.) K J 9 Interrogation 

G 7 Exclamation 

J and Iv are generally considered the most difficult 
letters in the alphabet. Do not separate J into double 











HINTS TO LEARNERS. 101 

N, and be careful that the dashes correspond in length. 
(See Exercise 2.) The figures 7 and 9 require care in 
spacing correctly. 

(9.) 0 R & 0 Z Y 

These are termed the “spaced letters,” and require 
great care in order to make them correctly. The 
“space” should be just double that ordinarily used 
between the elements of a letter. The usual tendency 
is to make it too great. It should be just sufficient to 
distinguish these characters from I, S and IT. 

157. The construction and manipulation of the alpha¬ 
bet having been thoroughly mastered by the practice 
of the foregoing exercises, it is now presented in its 
complete and consecutive form. 


A 

B 

0 

D 

E 

F 

G 

H 

I 

J 

K 

L 

M 

N 


I. Alphabet. 

0 - - 

P . 

Q —- 

R - - 

8 — 

m 

A — 

U — 

Y 

W _ 

X 

Y ~ - 
Z — - 
& 


1 - 

2 - 

3 - 

4 - 

5 - 


6 . 

7 - 

8 — 

9 - 

0 — 


II. Numerals. 





102 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


III. Punctuation, etc. 


* Period 
Comma 
Semicolon 
Interrogation 


Exclamation 
^Parenthesis 
Italics 
J Paragraph 


Numbers are always sent twice over, to avoid error ; 
once written out in full, and then in figures. In frac¬ 
tions one dot is used to represent the line between the 
numerator and denominator. 

158. It is necessary to again caution the student 
against falling into the common error—from which most 
books on the telegraph are not exempt—that is enter¬ 
tained respecting the elementary signs of the Morse 
alphabet. It is said to consist of two characters, the 
dot and the dash. The importance of the space is 
utterly ignored. The difference between good and bad 
sending is almost entirely a matter of spacing . A com¬ 
mon fault of young operators is to run their words too 
closely together. 

If the principles laid down in this work be firmly 
adhered to, the learner will be surprised, not only at 
the rapidity with which he masters what appears to be 
a very difficult lesson, but at the extreme accuracy with 
which he manipulates his instrument. He must also 
carefully bear in mind that one of the most universal 
faults, among those attempting to learn the telegraphic 
art, is that of going over a great deal and learning 
nothing well. 

159. Reading by Sound. —This can only be attained 
by constant and persevering practice, keeping in mind 
the principles above given. The lever of the Morse 
apparatus makes a sound at each movement, the down- 


* The Semicolon, Parenthesis and Italics are seldom used in this country. It is 
customary among operators to emphasize particular words by separating the letters 
more widely than ordinarily. 

f Preceding and following the words to which they refer. 

1 When this occurs the copyist makes a new paragraph, by commencing the 
next word upon auother line. 







HINTS TO LEARNERS. 


103 


ward motion producing the heavier one, or that repre¬ 
senting dots and dashes ; or, more properly, the heavy 
stroke indicates the commencement of a dot or dash 
and the lighter one its cessation. A dot makes as much 
noise as a dash, the only difference being in the length 
of time between the two sounds. Thus, if the recoil or 
lighter stroke be dispensed with, it would be impossible 
to distinguish E, T and L from each other. 

In learning to read by sound it is best for two per¬ 
sons to practice together, taking turns at reading or 
writing, and each correcting the faults of the other. 
The characters must first be learned separately, and 
then short words chosen and written very distinctly and 
well spaced, the speed of manipulation being gradually 
increased as the student becomes more proficient in 
reading. After becoming sufficiently well versed in the 
art to read at the rate of twenty-five or thirty words 
per minute, the best practice will be found in copying 
with a pen and ink from an instrument connected with 
a line employed in transmitting regular commercial 
messages, in order that the student may familiarize 
himself with the usages of the lines and the minute 
details of actual telegraphic business. 

In conclusion, the student is warned against falling 
into the common error of expecting great results from 
little labor. To become an expert operator requires 
much time and patience, and the most unwearied appli¬ 
cation. Remember, that whatever is worth doing at all 
is worth doing well. The time will seldom or never be 
found when a thoroughly competent operator cannot 
obtain immediate and remunerative employment, how¬ 
ever overcrowded the lower walks of the profession 
may have become. 


CHAPTER IX. 


RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 

160. The American Compound Wire. —This impor¬ 
tant improvement in telegraphic conductors, referred 
to in another part of this work (135), has, within two 
or three years of its first introduction, become so 
extensively used that it seems likely in time to work a 
complete revolution in the American system of line 
construction. This wire is composed of a core of steel 
enveloped in a sheathing of pure copper, and coated 
with an alloy, of which tin is the principal ingredient, 
which serves to protect the whole from oxidization. , 

The relative strength of this wire is more than 50 
per cent, greater than that of iron wire of equal weight, 
and its conductivity is also largely in excess of the 
latter. If we take, for example, a No. 8 galvanized 
iron wire, the gauge now usually employed in this 
country in the construction of the best lines, and 
compare it with a compound wire of nearly similar 
electrical capacity, the superiority of the latter will be 
manifest. 



Weight 
per mile. 

Tensile 

Strength. 

Conductivity. 

Polos 
per mile. 

Galvanized Iron Wire. (No. 81. 

375 

1091 

1 

35 

American Compound Wire (No. 8) . 

112 

514 

1.07 

23 


In the above table the average conductivity of a 
mile of No. 8 galvanized wire is taken as 1, as a standard 
of comparison. The last column shows the number of 
poles per mile which will give the same percentage of 
strain upon the. ultimate strength of the wire. In 
practice, however, it is safe to reduce the proportionate 
number of poles used for the compound wire, as the 






















RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 105 

steel core is much more homogeneous and less liable 
to fracture on account of flaws, than the iron wire. 

The advantages which arise from increased conduc¬ 
tivity of the line wire and the diminution of the number 
of points of insulation and support are fully treated 
upon in another part of this work. The mechanical 
advantages of the compound wire are also very great. 
The labor of handling and stringing a light wire is much 
less than when a heavy one is employed. In running 
the wires over buildings, a mode of construction which 
has become very common in all large cities, stretches 
may safely be made double the length of those taken 
with the ordinary wire, and yet with less strain upon 
the insulators. Another important point in favor of 
this wire is the imperishable nature of the copper, 
which is the exposed metal. It is well known that 
the zinc coating of galvanized iron wire is soon de¬ 
stroyed near the sea-coast, and from the effects of 
carbonic acid arising from the combustion of coal in 
cities (137). Copper, under the same conditions, 
remains wholly unimpaired. Many cases occur in the 
construction of lines in which transportation is an item 
of great expense. In such cases, wire of the same 
or greater conductivity than galvanized iron, weighs 
materially less, with no disadvantage whatever arising 
from its lightness. 

161. The following table exhibits the weight, size, 
and relative strength of compound wires, equivalent in 
conducting power to the ordinary sizes of iron wire 
used in telegraphic construction. 



Galvanized 

Iron Wire. 

1 

Compound Steel and Copper Wire. 

• 

o 

Weight 

Relative 

Weight 

Relative 

Size of 

Size of 

cZ 

per mile. 

Strengih. 

per mile. 

Strength. 

Steel Core. 

Compound. 

9 

318 

2.9 

99 

4.9 

16 

14 

8 

375 

2.9 

112 

4.6 

16 

14 + 

7 

449 

2.9 

121 

4 4 

16 

13- 

6 

525 

2.9 

147 

4.5 

15 

12- 


























106 


RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 


The term relative strength, used in the preceding 
table, is the quotient obtained by dividing the strain 
which would break the wire by its weight per mile. 

In constructing lines with the compound wire, much 
care should be used in making the joints so as not to 
separate the copper sheathing from the steel core, thus 
allowing moisture to penetrate to the steel and oxidize 
it. This may, however, be guarded against by care¬ 
fully soldering the joints. 

162. The Gravity Battery. —Several modifications 
of the Daniell battery (19), especially adapted to tele¬ 
graphic use, are finding much favor within the past few 
years. The most economical and generally useful of 
these improved forms is the gravity battery. The best 
arrangement is that known as the Callaud. Another 
combination very closely resembling it, and giving 
nearly as favorable results, is known in this country as 
the Hill battery. In these elements the porous cup of 
the Daniell battery is entirely dispensed with, the two 



solutions being prevented from mingling by the differ¬ 
ence of their respective specific gravities. The zinc 
plate of the Callaud element, in the form of a short 
hollow cylinder, open at both ends, is suspended in the 
upper portion of the containing jar, as shown in Fig. 
56, by means of three hooks projecting from its upper 
edge, resting upon the jar. A strip of copper rolled 
into a spiral form is soldered to a copper wire covered 
with gutta-percha, forming the positive pole and con¬ 
necting it to the zinc of the next element. 



























RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 


107 


163. The manner of setting up this battery is as 
follows : 

A sufficient quantity of soft water is poured into 
each jar to fill it to a point above the upper surface 
of* the zinc. The battery should now be placed in the 
position which it is to permanently occupy, unless this 
has been already done. After the connections are 
made and everything in readiness, about three-quarters 
of a pound of sulphate of copper in lumps of the size of 
a hickory nut or larger, is dropped in, taking care that 
it does not lodge upon the zinc. The solution of sul¬ 
phate of copper being of greater specific gravity, will 
remain at the bottom of the jar. The battery, after 
it is set up, should be kept on a closed circuit for 
about twelve hours, when its resistance will have become 
reduced so that the force will be available. As the bat¬ 
tery continues in action, the sulphate of copper solu¬ 
tion gradually becomes weaker and the zinc solution 
stronger. It is therefore necessary from time to time 
to add crystals of sulphate of copper, and to remove a 
portion of the zinc solution and replace by water. A 
good practical rule for maintaining this battery is to 
always see that the stratum of liquid around and in 
contact with the copper is kept of a blue color. The 
formation of transparent crystals upon the zinc indi¬ 
cates that the point of saturation of the zinc solution 
has been reached and that it should be diluted with 
water. A Baume hydrometer is very convenient for 
determining the density of the zinc solution. The latter 
should be maintained at from 20° to 30° in a main 
battery, and from 15° to 25° in a local. 

It often occurs in using this battery that stalactites 
of copper attach themselves to the lower edge of the 
zinc and hang suspended in the solution, slowly but 
constantly increasing in length. These are first pro¬ 
duced by a deposit of copper upon the zinc, which sets 
up a local action followed by a rapid decomposition of 
the solution and a further deposit of copper. These 
should be removed by means of a bent wire and allowed 


108 


RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 


to fall to the bottom of the jar, as they occasion a use¬ 
less expenditure of sulphate. 

Absolute quietude is essential to the proper per¬ 
formance of this battery. A slight jar will cause the 
solutions to mingle, and this effect will be followed by 
a rapid deposition of metallic copper upon the zinc. 
When the zincs are remov r ed for cleansing, care must be 
taken not to agitate the solution. 

Prof. Hough, of the Dudley Observatory, has sug¬ 
gested the use of sheet lead in the place of the copper 
spiral, as it is cheaper and more readily cut and formed 
into proper shape. There is no perceptible difference 
in the electro-motive force or in the resistance of the 
battery when lead plates are substituted for copper in 
this way. 

The electro-motive force of the gravity battery is 
the same as the Daniell, and the average resistance 
when in good working condition about three units. 

164. Siemens’ Universal Galvanometer. —The ap¬ 
paratus employed for the measurement of electrical 
resistances consists essentially.of a standard resistance, 
which is used for the purpose of comparison, a galva¬ 
nometer, by which the result is indicated, and a galvanic 
battery. In the different methods of testing, these 
appliances are arranged in various ways, as particular 
circumstances may render convenient or desirable. 
The various methods of testing in use may be classified, 
however, under three heads, viz.: 

1. By the angles of deflection of a galvanometer 
needle. 

2. By the differential galvanometer. 

3. By the Wheatstone bridge, or electrical balance. 

The first-named method is the simplest in principle, 

and, with proper care, gives very accurate results. It 
is not so convenient as the other two methods for ordi¬ 
nary use, but is applicable more especially for the 
measurement of very high resistances, such as insula¬ 
tors, etc. It is also employed in measuring the inter¬ 
nal resistance of batteries. As the strength of the 



RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 109 

current passing through the coils of a galvanometer is 
always proportionate to the sine or tangent of the angle 
of deflection of the needle, and is also inversely pro¬ 
portional to the resistance in circuit, it follows that if 
we find the deflection with a certain known resistance 
in. circuit to be only 22°, and we then substitute for 
this known resistance an unknown one, which gives us 
a deflection of 39°, the tangent of the latter will be 
twice that of the former, and the unknown resistance 
is consequently found to be half that of the known re¬ 
sistance. (170.) 

The second method is very convenient and is much 
used, although not equal in strict accuracy to the third 
method. The galvanometer coils are wound with two 
wires of the same length and resistance, insulated from 
each other with the utmost care. The needle is there¬ 
fore surrounded by an equal number of convolutions of 
each wire, which are also equidistant from it One 
end of each wire is connected to the battery, but in 
such a manner that the current flows in opposite direc¬ 
tions through the two wires. When, therefore, the two 
currents are of equal strength, one tends to deflect the 
needle to the right and the other to the left with equal 
power, and the needle remains at rest. If we insert 
an unknown resistance into the circuit of one of these 
wires the current is weakened, as is also its effect on 
the needle, which no longer remains balanced and at 
rest, but is deflected to one side. If we now insert a 
series of known resistances into the circuit of the other 
wire, until the needle is again brought into equilibrium, 
we are certain that the unknown resistance in one cir¬ 
cuit is exactly equal to the known resistance in the 
other. (122.) 

The third method is susceptible of the greatest accu¬ 
racy of measurement, when proper precautions are ob¬ 
served. The connections of the “bridge” are arranged 
as follows : 

We will suppose the wires A.BCD (Fig. 57), arranged 
in the form of a parallelogram, to be of exactly equal 


110 


RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 


resistance. If we attach the two poles of a battery, E, 
to the points 1 and 2, its current will divide at 1, half 
of it going through A B, and the other half going 
through C D, to the point 2, and thence to the other 
pole of the battery. The galvanometer Gr, placed on a 
wire connected across from 3 to 4, will not be affected 
as long as A B is equal to C D, no matter what the 
absolute resistance may be. 

Again, when A bears the same proportion to C that 
B does to 1), or when A: C: : B: D, no current will 
pass from 3 to 4 through the galvanometer. If the 
resistance of A be made 10, that of B 1, of C 1,000, 



and of D 100, the total resistance of A B will now be 
11. and that of C 1,100 ; but the tension in each 
branch will have fallen in the same proportion at the 
points 3 and 4, and no current will pass between those 
points. 

If, therefore, we insert a known standard resistance 
in the wire B, and an unknown one in 1), and divide a 
given resistance between A and C until we get no effect 
upon the galvanometer needle, we are then certain that 
tne resistance of A bears the same proportion to that 
of B as the known resistance does to the unknown one 
D, which may be readily calculated by proportion or 
the “ rule of three.'’ 

It is not necessary, of course, that the wires should 
be arranged in the exact form shown, nor in fact is it 











RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 


Ill 


often done, but the principle is more easily explained 
and remembered when thus arranged. 

165. The Universal Galvanometer of Dr. Werner 
Siemens is constructed upon the principle of the Wheat¬ 
stone bridge, just described, but its connections are so 
arranged that it may be used when desired for the 
method of deflections first mentioned. 

The galvanometer is mounted upon a disk of slate 
about six inches in diameter. A groove in the edge of 
this disk, extending about half way round the circum¬ 
ference, contains a wire of considerable resistance, 
which corresponds to the wires A and C in the above 
diagram. A small platina roller, mounted upon a 
radial arm, is connected to one pole of the battery, and 
forms the connection with the wire A C, as shown at 1 
in the diagram. The wire corresponding to B is sup¬ 
plied with three standard resistances of 10, 100, and 
1,000 Siemens’ units, respectively, either of which may 
be placed in circuit at pleasure, by means of contact 
plugs. The wire D is provided with binding screws for 
the attachment of the wire, or other resistance which 
it is required to measure. The galvanometer consists 
of a pair of very delicate astatic needles, suspended by 
a fine silk fibre. The coil has a resistance of 100 Sie¬ 
mens’ units. 

The radial arm carrying the platina roller also car¬ 
ries a pointer or index, moving over a scale upon the 
circumference of the slate disk, which is divided into 
300 degrees, and which may be read to one-fifth of a 
degree by means of a vernier. 

In using the instrument, the standard resistance cor¬ 
responding most nearly to the unknown resistance 
which is to be measured is unplugged and placed in 
circuit at B (Fig 57), while the unknown resistance 
itself is inserted at D. The radial arm carrying the 
platina roller 1 is now moved towards A or C, until 
the needle is balanced. The proportion of A to 0 is 
then read off the scale, from which the proportion ot B 


112 


RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 


to D is readily calculated, or is taken from a printed 
table furnished with the instrument. 

This galvanometer may also be employed for com¬ 
paring electro-motive forces, according to the method 
of Poggendorff,* and is applicable to almost any pur¬ 
pose for which an apparatus of the kind may be re¬ 
quired. 

This instrument usually has a constant of about four 
degrees, with one Danieli’s cell through 1,000,000 Sie¬ 
mens’ units. When used as a Wheatstone bridge, its 
range of measurement is from 0.17 to 59,000 Siemens’ 
units. Higher resistances, such as insulators, may be 
measured by the method of deflections. The entire 
apparatus (except the battery) occupies a space only 
nine inches in diameter, and the same in height. It is 
packed in a neat case, and can be carried about with 
great convenience. 

166. Pope & Edison’s Printing Telegraph. —Type¬ 
printing telegraph instruments, which were formerly 
employed for commercial telegraphing, have, within 
two or three years, been extensively introduced, in a 
modified and simple form, in * the various branches of 
private telegraphy, with great success. One of the 
best of these is that of Pope & Edison, which is used 
on a large number of private lines in New York city. 

The different portions of the apparatus, with the 
exception of the battery, are mounted upon a small 
table, similar in size and construction to that of an 
ordinary sewing-machine. At the back of the table 
are six binding screws to which are attached the line 
and ground wires, and the wires leading to the main 
and local batteries. The instrument operates upon 
what is known as the “open circuit principle,” each 
station transmitting with its own main battery—the 
line at the receiving station being connected directly 
through the relay to the ground without the interven¬ 
tion of a second battery. 

* See Clark’s ‘'Electrical Measurement,” p. 105. Also Sabine’s “Elect. 
Tel.,’’ p. 320. 




RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 113 


The printing apparatus is placed upon a circular 
iron base in the centre of the table. In front of it is 
placed a dial containing the letters of the alphabet, 
arranged in a circle and provided with an index or 
pointer, mounted upon a horizontal shaft. This shaft 
also carries a type wheel, with the letters of the alpha¬ 
bet engraved upon its periphery, and a scape-wheel, 

. with rachet-shaped teeth, corresponding in number to 
the characters upon the type wheel and dial. An 
electro-magnet beneath the base is provided with an 
armature, attached to a vibrating lever, the latter 
armed with pawls or clicks, so arranged in relation to 
the scape-wheel that every time the electro-magnet 
attracts its armature, the wheel is made to revolve a 
distance of one tooth, and the type wheel and index 
upon the same shaft a distance of one letter. At the 
extreme right of the circular base, and partly beneath 
it, as seen in the engraving, is placed a second electro¬ 
magnet, whose armature lever passes in a horizontal 
direction below the type wheel. Directly underneath 
the type wheel an india-rubber pad is fixed upon the 
lever, by means of which an impression of the letter 
which is opposite it upon the type wheel may be taken 
in the manner hereafter to be described. This lever is 
also provided with a simple mechanical device for 
moving the paper forward the proper distance, as the 
impression of each successive character is imprinted 
upon it. This may be seen at the left of the printing 
apparatus. The type wheel is provided with a suitable 
inking roller, as shown in the engraving. 

It will thus be understood that the printing mechan¬ 
ism is operated by two distinct electro-magnets, one 
of which is so arranged that its successive pulsations 
may be made to advance the index step by step to 
any required letter, while the other forces the strip 
of paper against the inked type upon the wheel, after 
it has been moved to the proper position by the first 
magnet. The type wheel is, of course, so arranged in 
reference to the index upon the same shaft, that when 


114 


RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 


the latter points to any given letter the correspond¬ 
ing letter upon the type wheel is opposite the impres¬ 
sion pad. 

These two electro-magnets are placed in the circuit 
of a local battery, which is brought into action by a 
relay placed in the main line circuit, as in the ordinary 
Morse apparatus. The relay is shown at the right of 
the printing mechanism, covered by a small glass 
shade. It is the same in principle as the ordinary 
Morse relay, with the addition of a device termed 
the “polarized switch ,’ 7 which consists of a perma¬ 
nently magnetized steel bar, pivoted between the jooles 
of the relay magnet, and forming a part of the local 
circuit. This is attracted to the right or left accord¬ 
ing to the polarity of the relay magnet, which itself, 
in turn, depends upon the direction of the electrical 
current in the main circuit. The polarized switch 
determines the direction of the local circuit, causing it 
to pass through the magnet for moving the type 
wheel, or through the impression magnet, as may be 
required. 

Two lever finger keys, with vulcanite knobs, are 
placed on each side of the printing apparatus, as 
shown in the engraving ; and it is by means of these 
that the instrument is operated. They are connected 
to opposite poles of the main battery in such a man¬ 
ner that, by depressing the right hand key, the posi¬ 
tive pole of the battery is connected, through the relay 
magnet to the line, and the negative to the ground, 
while the left hand key, on the contrary, sends a neg¬ 
ative current through the relay and line in the same 
manner. 

The mode of operating the instrument is exceed¬ 
ingly simple. By depressing the right hand key a 
sufficient number of times in rapid succession, a series 
of positive currents is sent through the relays at both 
ends of the line, which are repeated upon the local 
circuits of both instruments. The positive currents 
deflect .the polarized switches to the left, so that the 


RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 


115 


l 


local circuit is directed into the type-wheel magnet. 
The index and type wheel of both instruments, there¬ 
fore, advance one letter every time the key is de¬ 
pressed, and they may thus be readily brought to any 
desired letter. When this has been done, the left hand 
key is depressed, which sends a negative current, 
reversing the polarized switch, and the local circuit 
is directed through the printing magnet, producing 
the impression of that letter upon the strip of paper, 
and this process may be continued indefinitely. 

Suitable arrangements are provided for bringing the 
type wheels of the two instruments together in case 
they should accidentally be thrown out of correspond¬ 
ence. 

These instruments are entirely automatic in their 
action, and a despatch may be printed at the remote 
end of the line, in the absence of an attendant. In the 
event of any derangement of the printing apparatus, it 
may be used as a dial instrument as conveniently as if 
especially constructed for that purpose. 

The battery is always disconnected, except at the 
moment of working, and therefore is consumed but 
slowly. Other systems require the battery to be con¬ 
stantly connected to the line whether working or idle. 
A battery of two carbon cells per mile, and in many 
cases even less, will work the instrument and remain 
in action from one to four weeks without renewal, 
according to the amount of telegraphing done upon 
the line. 

It is impossible for the main circuit to be acciden¬ 
tally left open. Only one adjustment—that of the 
tension spring of the relay—is required after the 
instrument is first put in operation, and that but rarely 
on lines of ordinary length. 




CHAPTER I. 


APPENDIX AND NOTES. 


167. The Equipment of Telegraph Lines. —The 
satisfactory performance of any given telegraphic cir¬ 
cuit depends largely upon the maintenance of a proper 
relation between the respective resistances of the line, 
instruments, and batteries. There is in all cases an as¬ 
certainable definite proportion between these, which 
gives, theoretically, the best result with the least ex¬ 
penditure ; to which practice should always be made to 
approximate as nearly as possible. The disregard of 
the well-established laws of electrical and magnetic 
action is not only the source of grave difficulties in the 
practical operation of lines, but also entails an enor¬ 
mous waste of material and supplies. 

It is one of the fundamental laws of the electric cir¬ 
cuit, that with a given resistance of conducting wire and 
battery , the maximum magnetic force is developed when 
the total resistance of the coils of the electro-magnet or 
magnets is equal to the resistance of the other portions of 
the circuit, i. e., the batteries and conducting wires. (173.) 

The resistance of the conductor, which must of ne¬ 
cessity, always form a large proportion of the total 
resistance in every main circuit, is in practice deter¬ 
mined within certain well-defined limits, by considera¬ 
tions of distance, mechanical construction, and first 
cost. It therefore becomes necessary to adjust the 
resistance of the remaining parts of the circuit with 
reference to that of the conductor, which in practice 
usually ranges from 10 to 20 units per mile. With the 



APPENDIX AND NOTES. 


117 


No. 9 galvanized iron wire generally used, it approxi¬ 
mates closely to the latter figure. 

The resistance of the batteries forms but a very small 
portion of the total resistance in an ordinary main cir¬ 
cuit, and admits of comparatively little variation, so 
that the actual problem which presents itself, is to deter¬ 
mine the proper resistance of the relays when the 
resistance of the conductor is given, and the form of 
battery which will supply the necessary electrical power 
for operating the line with the least expenditure of 
materials and labor. 

The size of the conductor having been fixed upon, 
this taken in connection with the length will determine 
its total resistance. The combined resistance of the 
relays should be made to equal this amount as nearly 
as possible. It is hardly necessary to add that the re¬ 
sistance of the different relays should be uniform in 
respect to each other. With good relays the amount 
of battery required to operate the main circuit should 
not exceed 1 cell of Grove or Carbon battery for each 
150 units resistance, and will generally be less than 
this. About double this number of the Daniell, Hill, 
or Callaud battery will be needed. 

For example, suppose it is required to construct a 
telegraph line 300 miles in length, with 15 stations. 
If No. 9 iron wire is used as a conductor its resistance 
will be say 300 X 20 = 6000 units. The resistance of 
all the relays being made equal to that of the line, we 
have as the proper resistance for each relay - yf-° =400 
units. The amount of battery required will be 
=80 cups of Grove or Carbon, or about 160 cups of 
Daniell, Hill, or Callaud. 

The approximate average resistance, and compara¬ 
tive electro-motive force of the different batteries in 
use is as follows, the Grove battery being taken as the 
standard at 100 : 

Electromotive 
Resistance. force. 


Grove. 

Bi-Chromate or Carbon 

Daniell. 

Callaud .. 


.5 
1 0 
2.0 
3.0 


units. 

u 


100 

107 

56 

56 


U 

44 







118 


APPENDIX AND NOTES. 


These figures refer to the ordinary sizes of the Grove 
and Carbon battery, and to the Daniell and Callaud 
when adapted to a jar eight inches high and six 
inches inside diameter. Although the resistance of the 
battery when included in a single main circuit of the 
usual length, has but little influence upon the effec¬ 
tive strength of the current as a whole, yet in 
local circuits, and in main batteries from which a 
number of lines are worked at the same time (110), 
it becomes an essentially important element in the 
calculation. 

Another important law of electrical action, which 
applies especially to instruments which are to be worked 
by a local circuit, is the following : 

The greatest effective force of any given battery is 
developed when the sum of all the external resistances 
in the circuit is equal to the internal resistance of the 
battery. 

In a local circuit there are practically no resistances 
except those of the battery and magnet, and it is there¬ 
fore obvious that these should be so adjusted as to equal 
each other as nearly as possible. Tested by this rule, a 
great portion of the sounders, registers, and repeaters, 
in use in this country, will be found to have magnets 
of too low resistance, most of them being adapted to 
the use of a local of 1 Grove cell, although nearly all 
the local batteries in use are composed of 2 or 3 cells 
of Daniell. Such a magnet will only partially develop 
the effective force of a Daniell battery, and still less 
that of a Callaud or Hill. 

The sizes of copper wire generally used in local 
helices vary from No. 19 to 22, American gauge, and 
the resistance from 0.5 units to 4 units. The most 
usual resistance is about 1 unit. If we take a sounder 
of this resistance and apply a cell of Grove battery, we 
have the following result: 


Resistance of magnet. 1 unit. 

“ “ battery.1 “ 

Total.2 “ 





APPENDIX AND NOTES. 


119 


Calling the electro-motive force 100, and dividing 
this by the resistance, we get 50 as the effective strength. 
If we take the same sounder and apply a Daniell ele¬ 
ment with 2 units resistance the total resistance will be 
3, the electro-motive force 56, and the quotient or effec¬ 
tive force 18.6, but little more than one-third that of 
the Grove. With 2 Daniell cells we have— 


Resistance of magnet.. 1 unit. 

“ “ battery. 4 “ 

Total. 5 “ 


The electro-motive force of 2 cells will be 56 x 2 = 
112, and dividing this by the resistance, 5, we have 
22.4. With 2 Callaud cells the effect would be still 
less, in fact only 16. 

Now let us take the same sounder, and remove the 
helices of No. 19 wire, which give a resistance of 1 
unit, and rewind them with No. 23 wire, and observe 
the effect. With a given strength of current, the mag¬ 
netic effect is proportional to the number of convolu¬ 
tions, and the latter increase inversely as the square of 
the diameter of the wire. The resistance of the wire 
also increases as its length, and inversely as the square 
of its diameter. The squares of the respective diame¬ 
ters would be as follows : 

No. 19 .00128381 

“ 23.U0051076 

The average length of each convolution in a helix 
of a given size will be the same with any sized wire. 
The length being in inverse proportion to the square 
of the diameter, the resistance due to the increased 
length will be 

.00051076 : .00128881 : : 1 unit : 2.52 unite. 

But the resistance is further increased in inverse pro¬ 
portion to the square of the diameter of the wire, there¬ 
fore 

.00051076 : .00128881 : : 2.52 ; 6.3 








120 


APPENDIX AND NOTE3. 


6.3 units would, therefore, be the resistance of the 
new helices. This is not strictly accurate, as no 
allowance has been made for the spaces between the 
convolutions, which occupy more room in the coil 
when finer wire is used, and somewhat reduce the 
number of convolutions as well as the length and resist¬ 
ance of the wire. We will, therefore, call the resist¬ 
ance of the new helices 6 units. This resistance will 
give the greatest possible effect obtainable with 2 Cal- 
laud cells, which will be as follows: 

* T 

Resistance of magnet. 6 units. 

“ battery. 6 “ 

Total resistance... 12 “ 

Divide the electro-motive force 112 

- = 9.3 

By the total resistance. 12 

But the magnetic effect is increased by the greater 
number of convolutions in the proportion of the 
squares of the diameters, or as 2.52 to 1. Therefore 
9.3 x 2.52 = 23.43. This is greater than the magnetic 
effect of 2 Daniell cells upon the sounder of 1 unit 
resistance, which we before found to be 22.4. Making 
some deduction for the slight decrease in the number 
of convolutions, owing to the greater number of spaces, 
we may consider the actual magnetic effect to be the 
same in both cases. Experience has shown that this is 
amply sufficient to operate a well-constructed sounder 
or register. 

In the above calculations the resistance of the Daniell 
is given as 2 units. It is actually over 3, except when 
the porous cell is defective, or so excessively porous as 
not to separate the liquids properly. The Callaud is 
also given as 3 units, but in point of fact does not ex¬ 
ceed 2 after it has been 2 weeks in use. The resist¬ 
ance of the different Callaud cells is very uniform, 
while cells of the ordinary form of Daniell will often 
vary widely under precisely similar conditions. Some¬ 
times one cell will measure 10 units, and another 






APPENDIX AND NOTES. 


121 


only 2, owing principally to difference in the quality 
of the porous cups. A cell of high resistance will 
diminish instead of increasing the effect in a local 
circuit. 

The obvious advantage of using the Callaud battery 
for local circuits in connection with a magnet whose 
resistance is properly adjusted to it, consists in its great 
economy, the expense of maintenance not being more 
than one-fifth as great as when the ordinary Daniell 
is employed. The above calculations show that a 
great saving can be made when the Daniell itself is 
used, by regulating the resistance of the magnets to cor¬ 
respond with that of the battery. 

168. The Working Capacity of Telegraph Lines.— 
In order to secure the best possible result in the work¬ 
ing of telegraph lines we must keep down the resist¬ 
ance of the conductors in the circuit (42), and increase 
the resistance of the insulation (90) to the greatest 
practicable extent. In other words, the resistance must 
be as small as possible in the route we wish the electric 
current to travel, and as great as possible in every 
other direction. The practical ■working value of a tele¬ 
graph line is the margin between the joint resistance of the 
conductor and the insulation, and that of the insulation 
alone. The tension of the retracting spring of the 
relay armature, when upon a “working adjustment, 77 
is the measure of this margin or difference. It is evi¬ 
dent that this margin may be increased in two ways, 
viz. : 

1. By increasing the insulation resistance. 

2. By decreasing the resistance of the conductor. 

For example, suppose a line of telegraph 100 miles 
in length—the weather being rainy. Suppose that the 
conductor has a resistance of 20 units per mile, while 
the resistance of the insulators is 1,000,000 units per 
mile. Let the receiving magnet and battery be situ¬ 
ated at one extremity of the line and the key at the 
other. When the key is closed, the force acting upon 



122 


APPENDIX AND NOTES. 


the armature of the magnet is in proportion to the 
quantity of electricity leaving the battery and passing 
through the magnet to the line, and this quantity is 
made up of that escaping through the insulation along 
the line, in addition to that going through the con¬ 
ductor to the other end of the route. When the key is 
open, the force exerted upon the armature is due to the 
current passing through the insulation alone. The 
effective working strength is therefore the difference 
between the attractive forces acting upon the armature, 
when the key is opened, and when it is closed at the 
other end of the line—or, in other words, the working 
margin is the difference between the sum of the forces clue 
to the joint conductiv ity of the wire and insulators and that 
of the insidators alone (104). 

Thus, in the case cited: 


The total resistance of the wire is.. 2,000 units. 

“ insulation . 10,000 “ 

The joint resistance of wire and insulators is . 1,666 “ 


The strength of current being inversely proportional 
to the resistance, it will be as follows : 


When key at other end is closed. 100.00 

“ “ “ open. 16.66 

Difference, or effective working margin. . 83.83 

It is not the absolute resistance of the conductor or 
of the insulators that determines the value of a line. 
It is operated by the margin or difference between these 
two values (101). It is important that this should not 
be lost sight of. 

Now let us observe the effect of substituting a wire 
of twice the weight, having a resistance of only 10 
units per mile. We now have : 


Total resistance of wire . 1 000 units 

’* “ insulation (as before).. 10,000 “ 

Joint resistance. 909 “ 






















APPENDIX AND NOTES. 


123 


The proportionate strength of current will become : 

When key is closed. 100.00 

“ “ open. 9.09 

Difference... 90.91 

We have given the strength of current with key 
closed as 100 in both the above cases, in order to show 
the proportionate increase of margin. The absolute 
strength of current in the two cases is as 100 to 183, 
an increase of 83 per cent., while the increase of work¬ 
ing margin is only 9 per cent. 

We will now take the result of an actual measure¬ 
ment. A new No. 9 galvanized wire, 115 miles in 
length, on a clear and fine day, gave a resistance of 
2,400 units, or about 21 units per mile. On the same 
poles was a No. 10 plain wire, which had been in use 
nineteen years. This wire, including eight instruments 
in circuit, gave a resistance of 13,300 units. In a rain 
the insulation resistance of the good wire measured 
15,300 units, and the bad wire 19,050. 

The joint resistance of the good wire and its insula¬ 
tors was 2,077. The proportion of current escaping 
by the insulators was to the whole current as 13.51 to 
100, giving a margin to work on of 80.49. 

The joint resistance of the bad wire and its insula¬ 
tors was 7,982. The proportion of escape to the 
whole current was as 40 to 100, givingbut 00 percent, 
as an available working margin. This wire could not 
be worked except when the other circuits on the same 
poles remained idle, either closed or open. The good 
wire was worked without difficulty. The escape was 
apparent, but was not sufficiently great to cause any 
serious inconvenience. The relative working margins 
were in the proportion of 80.49 to 00. 

On a clear and cold day the insulation of the good 
wire showed a resistance of 2,400,000 units, the work¬ 
ing margin being 99.99. The bad wire showed an 
insulation resistance of 1,700,000 units, the working 
margin being 99.93. The difference in this case 






124 


APPENDIX AND NOTES. 


between the two wires was only 00.06, an amount not 
appreciable in practice. The poor wire worked as well 
as the good one, but the current was not so strong. 
This difference could be compensated for by increasing 
the battery on the former. 

In the above instance we have two wires on the 
same poles. One is new and a good conductor, the 
other old and a poor conductor. In fine weather the 
insulation of the new wire is the most perfect, but the 
difference in their working is inappreciable. In rain, 
although the insulation of the old wire is actually 
the best, yet it does not work nearly so well as 
the new wire, and this is attributable solely to the 
fact that the new wire has a much greater conductive 
capacity. 

Take another example, also from actual measure¬ 
ment : A new wire, 150 miles in length, on a clear 
day gave a resistance of 2,200 units. On the same 
poles was an old rusty No. 11 wire, which gave a re¬ 
sistance of 23,500 units. On a very wet day the insu¬ 
lation resistance of the new wire was 4,800 units, and 
of the old wire 32,000 units. The working margin of 
the new wire was 78, and that of the old wire 60. In 
this case the amount of current escaping over the 
insulators of the new wire was 2.7 times that passing 
through the old wire and its insulators combined ! In 
other words, the current with key open on the new 
wire was nearly three times as strong as on the old 
wire when the key was closed. 

In these examples the resistance of the batteries and 
instruments has not been taken into account, as they do 
not materially affect the results. 

169. The Electrical Tension of Telegraphic Bat¬ 
teries and Lines. —In another part of this work (8) it 
was briefly stated that the electrical tension of a battery, 
or its power of overcoming resistance, is increased in 
direct proportion to the number of elements of which 
the battery consists. Suppose we have a battery of 
100 cells, and the electro-motive force of each element 





APPENDIX AND NOTES. 125 

of this battery be such as to produce a difference in 
tension between its plates equal to 1, the difference 
between its poles or end plates will be equal to 100. 
But it must be understood that degrees of tension are 
only relative or comparative. The earth being our 
great reservoir of electricity, its tension is called zero, 
and it affords us a convenient standard of reference in 
comparing other tensions, but even the absolute tension 
of the earth sometimes varies in different times and 
places. 

Suppose we take the battery of 100 cells above 
referred to, place it upon a well-insulated stand, and con¬ 
nect one pole of it, say the zinc or negative pole, to 
earth, and leave the other pole disconnected, and there¬ 
fore insulated by the air. The end which is connected 
with the earth being in free communication with it, will 
now have a tension of zero, and the opposite end of the 
battery will have a tension of 100 positive, or above 
that of the earth, and if a wire were connected from it 
to the earth a powerful current of electricity will pass 
between them. 

If now the copper or positive pole be placed to the 
earth, and the zinc pole insulated, the tension of the 
former will now be zero, and that of the latter 100 
negative, or below that of the earth. In each of these 
cases the degree of tension is the same, but in one case 
it is above that of the earth, or positive, and in the other 
case below that of the earth, or negative. 

If the zinc or negative pole of the same battery be 
now connected to the earth, and the positive pole, in¬ 
stead of being left free, is connected by a short and 
thick wire, of no appreciable resistance, to the negative 
pole, the tensions throughout the circuit will be 
materially changed, although the electro-motive force 
will remain unaltered. The tension at the copper 
pole of the battery, which was 1,000 when the pole was 
entirely disconnected, now becomes the same as that 
of the earth, or at least but very little above it. If a 
wire offering considerable resistance be substituted for 


126 


APPENDIX AND NOTES. 


the short and thick wire which connects C and Z, the 
tension at C will be raised, although that of Z will still 
be kept at zero by its connection with the earth at that 
point. In proportion as the resistance of this connect¬ 
ing wire is increased, the tension at C rises until, when 
the resistance becomes infinite, the tension will again 
reach 100, for infinite resistance is absolute insulation. 
The tension is now equal to the electro-motive force, 
but it is obvious that it can never exceed it under any 
circumstances. 

If a battery of 100 cells is connected to a telegraph 
line of 100 miles in length, whose insulation is perfect, 
and which is not connected to the earth at the remote 
end, the line will instantly acquire a tension of 100 
throughout its whole length (this being equal to the 
electro-motive force of the battery), and this would oc¬ 
cur if the wire were a thousand or a million times that 
length. After the line has acquired the same tension 
as the pole of the battery to which it is attached, no 
current will flow from the battery. 

If the distant end of the line is connected to the 
earth, the battery will come info action, and a current 
of electricity will pass through it. This will at once 
change the tensions throughout the whole line. The 
distant end of the line, which originally had a tension 
of 100, will now have a tension of zero, being con¬ 
nected directly to the earth, and from this point the 
tension will rise gradually and regularly along the 
whole length of the line to the pole of the battery. 
So also the tensions within the cells of the battery 
itself follow the same law. 

The relation existing in a voltaic circuit between the 
resistances, electro-motive forces, and tensions, may be 
graphically and accurately represented to the eye by a 
geometrical projection based upon mathematical reason¬ 
ing, a method first suggested by Ohm, and more 
recently elaborated by Mr. F. C. Webb, and which he 
explains as follows: 

Let all the parts of a circuit, whether liquid or solid, 


APPENDIX AND NOTES. 


127 


be expressed in their successive order by portions of a 
continuous horizontal line, which shall be to one another 
as the reduced lengths or resistances of those parts. 
Let the tension at any given point in the circuit be 
represented by the perpendicular height of a point 
above, or depth below, the horizontal line representing 
the resistances. This when above the line will indi¬ 
cate a positive, and when below, a negative tension. 
The horizontal line of resistances may be termed the 
axis. 

In order to represent the tension at every point in 
the circuit, we must construct a line termed the line of 
tension. The perpendicular height of this line above 
the axis at any point, indicates a corresponding positive 
tension at that point, and its depth below in the same 
manner indicates a negative tension. When this line 
crosses the axis the point of intersection has no tension. 

Electro-motive force consists in a sudden and con¬ 
stant difference in the tension of the points situated 
immediately upon opposite sides of the surface of 
junction between the zinc element and the liquid of 
the battery. The electro-motive forces in the circuit 
must, therefore, be represented by a sudden rise in the 
line of tension at the points along the axis at which 
they occur, thus forming lines perpendicular to the 
axis. The magnitude of these lines must be propor¬ 
tional to the electro-motive force they represent. 
Moreover, as the electro-motive force is a quantity 
depending solely upon the nature of the elements at 
the surface of junction at which it occurs, and not at 
all on any change in the resistance or electrical state 
of the circuit, these perpendicular lines constantly 
maintain the same magnitude, although their posi¬ 
tion as regards the axis may be altered in various 
ways. 

Now let us construct a diagram which shall correctly 
represent the electro-motive forces, tensions, resist¬ 
ances, and strength of current, as a telegraph line with 
a closed circuit, having a battery of three cells at each 


128 


APPENDIX AND NOTES. 


end of the line, which will be a sufficient number to 
correctly represent the arrangement of the circuit or¬ 
dinarily used on American telegraph lines. 



Let the horizontal line N P' (see Fig. 59) represent 
the axis, or line of resistances, the latter being repre¬ 
sented in their respective order, beginning at the point 
of contact, N, between the extreme zinc plate of the 
battery and the liquid of the cell. N B, B C, and C 
P represent the respective internal resistances of the 
three battery cells, and X P that of the entire battery. 
Let P HF represent the resistance of the line wire, 
and N' P' that of the • battery at the opposite end of 
the line. Erect a perpendicular, N E, at the point N, 
and divide it into three portions, 1ST F, F Gr, and G E, 
which shall be to each other as the electro-motive 
forces at N, B, and C. The other battery, FP', having 
its negative pole, N', to the line, will give a negative 
tension; therefore a perpendicular P' E' let fall below 
the axis from the point P, and divided in the same 
manner, will represent the electro-motive forces of the 
battery N' P'. Therefore the line N P' represents the 
sum of all the resistances, and N E I P'E' the sum of 
the electro-motive forces. It necessarily follows 
that the line of tension, M H M', which we get by 
joining E and E', varies in the angle of its inclination 
to the axis according to the proportion between the 
sum of the electro-motive forces, IF E and P' E', and 























APPENDIX AND NOTES. 


129 


the sum of the resistances, N P'; and the degree of its 
inclination will therefore accurately represent the 
effective working strength of the current in all parts of 
the circuit. 

The varying tensions within the battery maybe cor¬ 
rectly represented as follows : Having joined E and E', 
erect perpendiculars at B and C and P. Now as the 
effective strength of current, represented by the incli¬ 
nation of the line E E', is the same at every point 
throughout the whole circuit, draw F I parallel to E Eb 
Then E I will be the line of tension in the first cell, 
falling regularly through the resistance of the liquid to 
the surface of generation, B, of the second zinc, where 
it rises suddenly to the extent of the electro-motive 
force there situated. Draw G- K parallel to E E', inter¬ 
secting B 0 at J. I J will then be equal to E G, 
which represents the electro-motive force at B, and J K 
will be the line of tension in tne second cell. Now as 
G K is parallel to E E' ; K L will be equal to G E, the 
electro-motive force at C, and L M will be the line of 
tension in the third cell. In the same manner the line 
of tension within the other battery N P'. 

The terminal points of the line N and P', being con¬ 
nected directly with the earth, their tension will be 
equal, and the same as that of the earth, which is 
assumed to be zero ; that is, neither positive nor neg¬ 
ative. It is manifest that at the point H, midway of 
the circuit where the line of tension crosses the axis, 
the tension is the same as that of the earth, or zero. 

In the illustration given, the line is supposed to be 
in a condition of perfect insulation. In actual practice 
there isaleakage at every support throughout the whole 
length of the circuit. The line of tension in this case 
would form a double catenary curve, its angle of incli¬ 
nation to the axis constantly increasing from H to M 
and Mb because in an imperfectly insulated or leaky 
line the current continually increases in strength in each 
direction from the neutral point to the battery poles 
at P and N'. 


130 


APPENDIX AND NOTES. 


Mr. Webb has demonstrated the correctness of the 
above method of geometrical projection by applying 
Ohm’s formula for obtaining the tension at any point 
of the circuit. The results are found to correspond in 
every case. This formula may be stated as follows : 

Let T = the. tension at any given point of the circuit a. 

Y = the abscissa of that point x, taking as origin the point of 
least tension. 

A = the sura of the electro-motive forces. 

L = the reduced length or resistance of the entire circuit. 

O = the sum of the electro-motive forces included in Y. 

C = the tension of the whole circuit to external objects. That 
is to say, the tension of the circuit, if it be an insulated 
circuit, and electrified by a source not contained within 
it. 

Then T=^Y-0-fC. 

XI 

As, in the case under consideration, the earth forms 
part of the circuit, the constant C disappears and the 
formula becomes 

t = £ Y — o. 

Ju 

Now take a point x in the diagram, and the tension 
x.x' will be found to agree with the formula. 

The quantities in the formula are thus represented 
geometrically in the figure : 

a = N E 
L = NH 
O = x' x" 

Y = x II 
T = x x' 

Now since the triangles H N E and H x x" are sim* 
ilar, we have 

N H : N E : : h x : a a" 

N E 

Consquently x x" = ^-g H x, 

and J K being parallel to 0 L, we have 

a' x" = K L. 


But x x = x x" — x' x" ; 

N E 

Therefore x x' = g-g H X — a* a", 


T = £ Y — 0. 

Ju 


Or, 





















APPENDIX AND NOTES. 


131 


An experimental proof of the above theory of ten¬ 
sion may be obtained by connecting a wire from the 
neutral point in the middle of the closed circuit of a 
telegraph line, and inserting a galvanometer or relay. 
It will be found that no current passes between the 
line and the earth, which proves that the electric ten¬ 
sion or potential at that point is zero, or the same as 
that of the earth itself. 

170. Double Transmission. —One of the most inte¬ 
resting problems in practical telegraphy is that of double 
transmission, or working in opposite directions at the 
same time over a single wire. This apparently para¬ 
doxical result may be accomplished in several different 
ways, the principles involved being very simple and 
easily understood. The method shown in the accom¬ 
panying diagram is that of Siemens & Halske, of Ber¬ 
lin, Prussia ; the apparatus now used in this country 
differing slightlv from it in some of its minor details. 

c 1 t- 



Fig. 60. 

A and B (Fig. 60), are the two terminal stations of 
the line. The main battery E, at station A, is placed 
with its + , and the battery E at station B with its 


























132 


APPENDIX AND NOTES. 


pole to the line, as represented. M and M' are the 
receiving magnets or relays, which are wound through¬ 
out with two similar wires of equal length, as shown in 
the figure, whose connections will hereafter be explained. 
The rheostat or resistance, X, must be adjusted so as to 
be exactly equal to that of the line A, B, added to that 
of the relay wire 7, 5, at the other station. Similarly 
X' is also made’ equal to the line including the relay 
wire 3, 1. 

If, now, the key K at station A be depressed, the 
current from the battery E will divide at the point 1, 
one portion going through the relay coils to 3, over the 
line A, B to 7, and thence through the relay M' to 5, 
key lever 6', and contact C' to the earth at G', and the 
other portion in an opposite direction through the relay 
coils from 2 to 4, and thence through the resistance X 
to the negative pole of the battery. These two cur¬ 
rents will be equal to each other, the resistance being 
the same by each of the two routes, as before explained, 
but as they pass in opposite directions through the two 
wires surrounding the relay M, they produce no mag¬ 
netic effect upon it. The relay at B, however, will be 
affected by the current coming from A through the 
wire 7, 5, and will give signals corresponding to the 
movements of the key at that station. 

If, now, the key at B be also depressed, the same 
action takes place ; one half the current passes over 
the line, combining with the current from A, and the 
other half returns to the battery through the other 
wire of the relay and the rheostat. 

The relay wires 1, 3 and 7, 5 are now traversed by 
the double current, equal to § + £, but the wires 2, 4 
and 6, 8 are traversed only by the current of a single 
battery, having at A the force of £ and at B the force of 
?. The latter current being in the opposite direction to 
the former, the relays at both stations are affected by 
the difference in the forces of these currents, the relay 
at A by (£+?) — and the relay at B by (£+?) — f. 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


133 


Thus each station receives its signal through the action 
of the distant battery only. 

In the arrangement shown in figure 60 a third posi¬ 
tion occurs, where one of the keys, at E for instance, 
is in the act of changing from the front contact A' to 
the rear contact C', or vice versa , in which case the cur¬ 
rent from A is interrupted at B', and therefore passes 
through the second wire of the relay 6, 8, but this time 
in the same direction, and thence through the rheostat 
X' to the ground. The current arriving at B is con¬ 
siderably weakened in consequence of the additional 
resistance encountered at X', but this is compensated 
for by its passing through both wires of the relay M in 
the same direction, and its action upon the relay, there¬ 
fore, remains about the same as before. 

One slight difficulty, however, arises in this connec¬ 
tion. It will be seen that when the current at the 
receiving station is thus momentarily thrown through 
both relay wires and the rheostat, it must necessarily 
cause an unequal division of the current between the 
two opposing relay wires at the sending station, as the 
resistance of the long circuit becomes about double that 
of the short one. This effect is avoided in the Ameri¬ 
can system by a modification of the transmitting appa¬ 
ratus, which is operated by the lever of a sounder placed 
in a local circuit in connection with the key. When 
the local circuit is closed the downward movement of 
the sounder lever makes the battery connection upon 
a flat spring, and the movements thus imparted to the 
spring breaks the earth contact. The spring being at¬ 
tached to the line wire the connection is necessarily 
always complete, either direct or through the battery, 
and it is not obliged to pass through the rheostat when 
the transmitter is changing from the battery to the earth 
contact, or vice versa. The disadvantage in this case 
arises from the fact that the main battery is thrown on 
short circuit at each movement of the transmitter, ren¬ 
dering it necessary to interpose a considerable addi¬ 
tional resistance between the back contact and the bat- 


134 


APPENDIX AND NOTES. 


tery, to prevent the rapid consumption of the latter 
which would otherwise ensue. These improvements 
were devised by Mr. J. B. Stearns. 

In working this system, it is necessary to keep the 
rheostat so adjusted that its resistance will correspond 
exactly with that of the line, as above shown. If the 
relay works too feebly the counter current must be 
weakened by increasing the resistance of the rheostat. 
If the magnetism is too strong the resistance should be 
diminished. A careful study of the diagram will show 
that this system operates equally well, whether similar 
or opposite poles of the two batteries are placed to¬ 
wards the line. With like poles the action will be as 
follows: 

If the key at A be depressed, the current on the 
line will be £ and through the rheostat £, neutralizing 
each other upon the relay of A, but giving a current 
of f in the relay at B. Now, if the key at B be also 
depressed, a current equal to g is thrown through each 
wire of his relay, but the current J being equal and 
opposite to | the current of the main line will — 0. 

The current through the second wire of the relays 
being still unaffected, each relay will give a signal cor¬ 
responding to the time the key at the other station is 
depressed. 

171. Edtson's Button Repeater.— This is a very 
simple and ingenious arrangement of connections for a 
button repeater, which has been found to work well in 
practice. It will often be found very convenient in 
cases where it is required to fit up a repeater in an 
emergency, with the ordinary instruments used in 
every office. Fig. 61 is a plan of the apparatus. 

M is the western and M' the eastern relay. E is the 
main battery, which, with its ground connection Gf, is 
common to both lines. E' is the local battery, and L 
the sounder. S is a common “ ground switch,” turn¬ 
ing on two points, 2 and 3. In the diagram the switch 
is turned to 2, and the eastern relay, therefore, repeats 
into the western circuit, while the western relay ope- 



MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


135 


WEST 



I'-Lli. 61 


rates the sounder, the circuit between 1 and 2 through 
the sounder and local battery being common to both 
the main and local currents. If the western operator 

breaks the relay 
M opens, and con- 
EAST sequently the soun¬ 
der, L, ceases to 
work. The opera¬ 
tor in charge then 
turns the switch to 
3, and the reverse 
operation takes 
place; the western 
relay repeats into 
the eastern circuit, 
and the eastern 
relay operates the 
sounder. The soun¬ 
der being of coarse wire, offers but a slight resistance to 
the passage of the main current. 

172. Bradley’s Tangent Galvanometer.— The com¬ 
mon galvanometer used for the measurement of elec¬ 
tric currents consists of a magnetized steel needle, 
suspended in the centre of a hollow frame covered with 
insulated copper wire. The degree of deflection of this 
needle from its normal position in the magnetic meridian, 
when a current is passing, indicates the strength of the 
current. In the ordinary galvanometer, however, the 
angle through which the needle is moved, or in other 
words, the number of degrees over which it passes, is not 
an accurate measure of the strength of the current when 
the deflection exceeds 15°, for the further the needle 
moves from a position parallel to the wires of the coil 
the more nearly does it approach a right angle, in which 
position the effect is null, so that the action of the cur¬ 
rent upon it becomes less and less powerful as the de¬ 
viation increases. Several arrangements have been 
tried in order to obviate this objection, the most com¬ 
mon being that of a ring having a groove on its edge 








































136 


APPENDIX AND NOTES. 


filled with wire. The needle is hung precisely in the 
centre of the ring, and must not be longer than one 
sixth of its diameter—a half inch needle requiring a 
three inch ring. The needle is then deflected with a 
force varying as the tangent of the number of degrees 
through which the needle moves. Owing to the great 
distance of the coil from the needle, this arrangement 
has very little sensitiveness compared with the common 
galvanometer. 

In Bradley’s Galvanometer a compound needle is 
employed, composed of several needles of thin, flat 
steel, fixed horizontally upon a light flat ring of metal, 
forming a complete circular disc of needles, having an 
agate cup in the centre, to rest upon the pivot upon 
which it moves. At each extremity of the meridian 
light points project, to indicate the degrees of deflection. 
This compound needle, after having been magnetized, 
is planed within or over a coil whose breadth is exactly 
equal to the diameter of the disc. This compound cir¬ 
cular needle, being under the influence of the same 
number of convolutions of the coil in all its deflections, 
fulfils the required conditions for a true tangent gal¬ 
vanometer. 

The theorem, “ The intensity of currents, as measured 
by the tangent galvanometer , is proportional to the tangents 
of the angles of deflection f may be verified in the fol¬ 
lowing manner: 

Call the terrestrial magnetism, whose tendency is to di¬ 
rect the galvanometer needle to the magnetic meridian, 
the unit of directive force, and let this unit be represented 
geometrically by the line A M (Fig. 62), which is the 
radius of the circle M B M—the line M A M representing 
the meridian. When there is no other force acting on the 
needle its direction is with the meridian. Now let an 
electric current be sent through the galvanometer coil, 
whose directive force is precisely equal to the terrestrial 
force, and whose tendency is to direct the needle in 
a line perpendicular to the meridian, and let this force 
be represented by the line A B. 



MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


137 


M 


If the terrestrial force could now, for a moment, be 
suspended, the needle would point due cast and west; 

Tam's but the combined action of 
the two equal forces will 
direct the needle toward 
the point of intersection of 
the line drawn perpendic¬ 
ularly from M, and that 
drawn horizontally from B, 
at 1, which direction cuts 
the quadrant at 45°, the line 
M 1 being the tangent of 
45°, which is 1. 

Now, if we augment the 
intensity of the current 
through the coil to twice 
its present force, which will 
be 2, and will be represen¬ 
ted by the line A C, the 
combined forces A M and 
A C will direct the needle 
toward the point 2. If we 
now lay a protractor on the 
circle, we find that the line A 2 cuts it about 63° 30', of 
which the tangent is 2. 


E 

D 

1 * 

1 


o 


V 

M / 

1 9 / / 

r-/ 0/ 

/N <*>/ 

K / W ' 

N / / co/ 

B 


11/ • X 

/ yOy 


.25 

.125 

M 


Fig. 62. 


We may increase the parallelogram erected upon A 
M at pleasure, and the two forces combined will 
always so balance the needle between them as to make 
it point from A, diagonally, across the parallelogram 
to its opposite angle, the height of which is the tangent 
of the angle of deflection. 


By inspection of the diagram it is seen that the law 
holds good in the subdivisions of the force A B, as at 
.5 .25 and .125, a truth admitted by all experimenters, 
as to the relations, up to 14°. 

173. Thompson’s Reflecting Galvanometer. —This 
is the most delicate apparatus of this kind which has 
yet been devised, and is for this reason employed in 
operating the Atlantic Cables. 










138 


APPENDIX AND NOTES. 


The special feature which distinguishes this galvan¬ 
ometer from an ordinary one, is the extreme lightness 
of the magnet or needle, and the delicacy with which 
it is suspended in a horizontal position. Instead of an 
index needle, to render the motions of the magnet visi¬ 
ble to the eye, a reflected ray of light is made use of, 
which, of course, can be made of any required length. 
This arrangement is of great practical value in mea¬ 
suring faint electrical currents, too feeble to be indicated 
by any other apparatus. It is especially valuable in 
submarine telegraphing, because it permits the use of 
such extremely low battery power. 

When the insulation of a cable is in the slightest 
degree defective at any point, a current of intensity 
has a tendency to aggravate the fault, and to corrode 
and eat away the conductor by chemical decomposi¬ 
tion, at the point where the escape occurs, finally des¬ 
troying the communication altogether. 

Fig. 63 is a side elevation of this instrument, show¬ 
ing a section through the galvanometer coils and the 
outer case containing them. Fig. 64 is a cross section 
through the coils, showing the magnet, technically 
termed the needle. Similar letters refer to like parts 
in both figures. The magnet A is a small bar of steel, 
one half inch in length and one tenth of an inch square, 
cemented to the back of a very thin circular glass mir¬ 
ror, a. The mirror is suspended in a brass frame, B 
(Fig. 64), by an exceedingly delicate silk fibre, and is 
adjusted in height by the screw b. This frame slides 
into a vertical groove left in the centre of the coil, 
dividing it into two parts. The coil and mirror are 
enclosed in the brass case D, this case having pieces of 
glass let in wherever necessary, to permit the passage 
of light. The object of this arrangement is to pre¬ 
vent the mirror and its attached needle from being dis¬ 
turbed by currents of air. 

A narrow pencil of luminous rays from the lamp, E, 
passes through the opening, F, which is capable of ad¬ 
justment by the slide Gr. This pencil of light, passing 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


139 


through the lens, is reflected by the mirror back through 
the lens upon an ivory scale at I, as shown by the dot¬ 
ted lines. The scale is horizontal, extending to the 


f 





right and left of the centre of the instrument, the zero 
point being exactly opposite the lens, lho luminous 
pencil is brought to a sharp focus upon the scale by a 











































































140 


APPENDIX AND NOTES. 


sliding adjustment of the lens M, in the tube X. When 
the needle is at rest in its normal position, and no cur¬ 
rent is passing; the spot of light which serves as an in¬ 
dex will remain at zero on the scale. 

The operator reads the signals from a point just in 
the rear of the magnet and coils, the light of the lamp 
being cut off by the screen Y, so that he only sees the 
small luminous slit through which the light enters the 
instrument, and a brilliantly defined image of the slit 
upon the white ivory scale just above, which is kept in 
deep shadow by the screen Y. A very minute dis¬ 
placement of the magnet gives a very large movement 
of the ray of light on the scale I, the angular dis¬ 
placement of the ray of light being double that of the 
needle. 

It is obvious that the ray of light from the needle 
will be reflected to the right or left of zero on the scale, 
according as the deflection is produced by a positive or 
negative current. The Morse alphabet is used for sig¬ 
naling through the Atlantic cable, deflections on one 
side of zero indicating dots, and on the other side 
dashes. 

It will be observed that the end, and not the broad 
part of the flame of the lamp, is presented to the slit 
F, which is also arranged to receive the brighest part of 
the vertical section of the flame. 

The galvanometer coils, R, consist of many thousand 
convolutions of fine insulated copper wire, and they 
are insulated from the case, D, by a disc of hard rub¬ 
ber, T, to which they are fastened. 

The instrument is usually provided with a directing 
magnet, by which its sensitiveness may be varied to a 
great extent. This magnet is in the form of a bar, 
slightly curved, and is of considerable power. It is 
placed upon a vertical rod passing through its centre, 
which is fixed above the coil immediately over the 
needle, in such a manner that it can be turned horizon¬ 
tally so as to follow the movements of the needle, or 
be removed nearer to or further from it vertically. If 



MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


141 


it is placed with its south pole over the north pole of 
the needle, it will add its directive force to that of the 
earth, and by holding the needle more powerfully in 
its position, will lessen its sensitiveness. The nearer 
the magnet approaches the needle the greater will be 
its power over it, and it can be arranged so as to hold 
the needle in any desired position. If it is placed in a 
reverse direction, so as to repel the needle instead of 
attracting it, it will lessen the attractive force of the 
earth so as to increase its sensitiveness, and in a cer¬ 
tain position will render the galvanometer astatic. 
When the magnet is too near the needle it repels to 
the full extent of the scale. If it is raised upon the 
supporting rod the repelling effect will decrease, until, 
at a certain distance from the magnet, the spot of light on 
the scale can be held at zero. The greatest sensibility 
is obtained at the point at which the slightest lowering 
of the magnet upon the rod will again repel the needle 
to the full extent of its swing. 

An improvement in this instrument, made by Mr. C. 
F. Yarley, consists in giving the mirror a concave form, 
silvered upon the back, and thus dispensing with the 
use of the lens above described. 

174. Mode of Working the Atlantic Cables.— 
Very little has been made public in regard to the pre¬ 
cise method employed in signaling through the Atlantic 
cables. As before remarked, the reflecting galvanome¬ 
ter is employed as a receiving instrument, and by em¬ 
ploying deflections on one side of zero to represent 
dashes, and those on the other side dots, the Morse 
alphabet is found to answer the purpose admirably. It 
is said that the two cables have been looped in a metallic 
circuit without ground connection, and that they have 
also been worked separately with and without conden¬ 
sers. The latter method is made use of in order to 
avoid the disturbances generated by what arc known 
as “ earth currents.” 

Different parts of the earth and sea are found to be 
at different electric potentials. One part is electro- 


142 


APPENDIX AND NOTES. 


positive or electro-negative to another. That is to say, 
there is the same difference between the two parts of 
the earth that exists between the two poles of a bat¬ 
tery. If, therefore, these two points arc joined by a 
wire, a current will flow through that wire as if from a 
battery, and this current is termed an earth current, to 
distinguish it from the current generated by an ordi¬ 
nary voltaic battery. This difference of potential be¬ 
tween two given points, such as Newfoundland and 
Valencia, is not constant but continually varies, causing 
a corresponding variation in the current it produces. 
This current and its fluctuations interfere with the sig¬ 
naling current, disturbing the distinctness of the sig¬ 
nals. When very rapid changes take place in the elec¬ 
tric condition of the earth, it is known as a magnetic 
storm, and this occasionally interferes with the work¬ 
ing of all telegraph lines. 

By the method of working with condensers the dis¬ 
turbances from this cause are avoided. The condenser 
is constructed of alternate layers of tin foil and thin 
plates of mica, gutta-percha or paper, saturated with 
paraffine, arranged like the leaves of an interleaved 
book. Each alternate metal plate is connected so as to 
form two distinct series, insulated from each other, one 
of which is connected with the line and the other with 
the earth. By an inductive action, similar to that of 
the well known Leyden jar, a quantity of electricity, 
in proportion to the amount of surface exposed, may be 
accummulated or stored up upon the metallic plates. If, 
therefore, one series of plates be charged with positive 
electricity the other series will become negative by 
induction, and by means of this induction a much 
larger quantity of electricity may be accumulated than 
would otherwise be the case. 

The manner in which the condenser is made use of in 
working a cable is as follows: 

The sending apparatus consists of a battery, B (Fig. 
65), which is permanently connected with the cable 
through the back contact of a Morse key, K, and the 


MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


143 



cable is therefore kept constantly charged from this 
battery. When the key is depressed the cable is 
placed in connection with the earth at E. The receiv¬ 
ing apparatus consists of the reflecting galvanometer 
G (1G3), one terminal of which is attached to the cable 
and the other to one scries of plates in the condenser 

C—the other series 
being connected with 
the earth, as shown 
in the figure. It is 
a very high resist¬ 
ance, inserted in a 
wire leading from 
the point 0, between 
the cable and the 
galvanometer, so as 
to allow a very slight but constant leakage from the 
cable to the earth. The cable is, therefore, charged to 
the tension of the battery B, and the condenser to a 
tension equal to that of the point 0—but owing to the 
high resistance at R the tensions are nearly the same. 
Upon charging the cable with the battery at Iv a charge 
of electricity enters the cable, and a quantity sufficient to 
charge the condenser passes through the galvanometer, 
deflecting the mirror until the condenser is charged 
equal to the tension of the point 0—when the mirror 
will return to zero. By putting the cable to earth at 
K a portion of the charge will be withdrawn, and the 
tension of the point 0 lowered below that of the con¬ 
denser. A portion of the charge of the latter, there¬ 
fore, flows into the cable, deflecting the galvanometer in 
the opposite direction. The right and left hand deflec¬ 
tions necessary for signaling are therefore produced with¬ 
out reversing the currents, or rendering it necessary to 
entirely discharge the cable after each signal. This 
mode of signaling possesses many important advan¬ 
tages over the old method, in point of rapidity of action 
and freedom from interference by earth currents. The 
rate of working through the cable by expert operators 

























144 


APPENDIX AND NOTES. 


is said to average from fifteen to twenty words per 
minute. 

175. Telocity of Electric Signals. —For many 
years the velocity of electric signals in passing through 
a conductor was supposed to be infinitely great, or at 
least so great as to be incapable of measurement. In 
1849, Professor Sears C. Walker, of the United States 
Coast Survey service, while engaged in measuring 
longitude by means of the electric telegraph, discovered 
a perceptible retardation. Experiments between Wash¬ 
ington and St. Louis indicated a velocity not far from 
16,000 miles per second. Some of the measurements 
w r ere as low as 11,000 miles per second. On the even¬ 
ing of the 28th of February, 1868, a number of experi¬ 
ments were made by the officers of the Coast Survey, 
for the purpose of determining accurately the difference 
in longitude between Cambridge, Mass., and San Fran¬ 
cisco, Cal. A wire was connected from Cambridge to 
San Francisco and back, embracing thirteen repeaters—- 
the whole distance thus traversed by the signals being 
about 7,000 miles. 

The following table shows tlie time, in hundredths of 
a second, occupied by a signal in passing from Cam¬ 
bridge to each of the repeating stations and back. The 
number of repeaters in circuit is also given: 

TIME OF TRANSMISSION FROM CAMBRIDGE. 

To Buffalo and Return 
“ Chicago “ 

“ Omaha “ 

“ Salt, Lako “ 

“ Virginia City “ 

“ San Francisco “ 

The actual time of transmission from Cambridge to 
San Francisco and back was estimated not to exceed 
three tenths of a second, the “armature times” of the 
thirteen repeaters probably amounting to four or five 
tenths of a second. 

In submarine cables the velocity of signals is con¬ 
siderably less than upon air lines. Prof. Gould, in his 


Seconds. 

0.10 1 Repeater. 

0.20 3 “ 

0.33 5 “ 

0.54 9 “ 

0.10 11 “ 

0.74 13 “ 










MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


145 


experiments upon the. Atlantic Cable, found it to be 
between 7,000 and 8,000 miles per second—being 
greater when the circuit was composed of the two 
cables, and less when the earth formed a part of the 
circuit. His experiments seemed to show that, instead 
of travelling around the entire circuit in one direction, 
the electric wave, or polar influence, travelled both 
ways from the battery, and the signal w T as received 
when the two influences met. Experiments made on 
air lines indicate that an instrument placed at the cen¬ 
tral point of resistance between the two poles of the 
battery will record the signal sooner than when placed 
in any other part of the circuit, it being understood 
that the two terminal batteries of a telegraph line are 
in effect but one, being connected by the earth, which is 
a conductor of infinitely small resistance. 

176. Speed of Transmission. —The average rate of 
transmission, by the most skilful operators upon the 
Morse apparatus, is about 1,800 words per hour. This 
has been considerably exceeded, however, by many 
operators within the past two or three years. On the 
evening of January 28th, 1868, 2,520 words of Press 
news were sent from New York to Philadelphia in one 
hour, and legibly copied by the receiving operator, 
without a stop or break—the average rate being forty- 
two, and the maximum rate forty-six words per minute. 
On the 7th of February following 2,630 words of Press 
news were sent from Milwaukee, Wis., to St Paul, Minn., 
in one hour, the distance being about 400 miles. On 
the 19th of the same month 1,352 words of Press news 
were sent from New York to Philadelphia in thirty 
minutes, the average rate being over forty-five words 
per minute. 

This is believed to be the quickest time on record 
which has been made in the transmission of regular 
business by the Morse system. The receiving opera¬ 
tor, in all the above cases, copied entirely from the 
sound of the instrument. 

The speed of the printing instrument exceeds that 





146 


APPENDIX AND NOTES 


of Hie Morse under favorable circumstances. On the 
24th of September, 1867, the Combination instrument 
transmitted from Albany to New York 1,453 words of 
Press news in thirty-three minutes. It is claimed that, 
on some occasions, as many as 2,900 words per hour 
have been transmitted by the House instrument. 

177. Comparison of Wire Gauges. —The different 
sizes of wire employed for telegraphic and other pur¬ 
poses arc designated by a series of arbitrary numbers. 
The system known as the Birmingham gauge is the one 
in most general use at the present time, but is objec¬ 
tionable, both on account of the irregularity of its gra¬ 
dations and the absence of any authorized standard— 
wire of the same number from different makers often 
varying considerably in its size. The American gauge 
is formed upon a geometrical progression, and it is to be 
hoped will eventually supersede the old gauge : it is 
already employed to a considerable extent.* The fol¬ 
lowing table gives the diameter, in thousandths of an 
inch, of each number in the American and Birmingham 
gauges: 

TABLE OF DIAMETEftS OF WIRES. 


Number. 

American 

Gauge. 

Birminghar 

Gauge. 

0000 

,. 4 G 0 

.454 

000 

.40964 

.425 

00 

.36480 

.380 

0 

.32495 

.340 

‘1 

.28930 

.300 

2 

.25703 

.284 

3 

.22942 

.259 

4 

.20431 

.238 

5 

.18194 

.220 

G 

.16202 

.203 

n 

.14428 

.180 

8 

. 12 S 49 

.165 

9 

.11443 

.148 

10 

J 10189 

.134 

11 

.09074 

.120 

12 

.08081 

.109 

13 

•07196 

.095 

14 

.06408 

.083 

15 

.05707 

.072 

16 

.05082 

.065 

17 

.04526 

.058 

,18 

.0403 

.049 


mber. 

American 

Gauge. 

Birmingham 

Gauge. 

19 

. 035 S 9 

.042 

20 

.03196 

.035 

21 

.02846 

.032 

22 

.02535 

.028 

23 

.02257 

.025 

24 

.0201 

.022 

25 

.0179 

.020 

26 

.01594 

; oi 8 

27 

.01419 

.016 

28 

.01264 

.014 

29 

.01126 

.013 

30 

.01002 

.012 

31 

.00893 

.010 

32 

.00795 

.009 

33 

.00708 

.008 

34 

.0063 

.007 

35 

.00561 

.005 

36 

.005 

.004 

37 

.00445 

• * • • 

38 

.00396 

• • • • 

39 

.00353 

• • • • 

40 

.00314 

• • • • 


* This gauge is manufactured by Darling, Brown & Sharpe, of Providence, R. I 





















MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


147 


178. Useful Formulae for Weight and Resistance 
of Wires. —The following formulae, from Clark’s tables, 
will be found convenient in telegraphic work: 

The weight of any iron wire, per statute mile of 5280 
feet, is tIVs lbs.; dr denoting the square of the diame¬ 
ter of the wire in“ mils” or thousandths of an inch. 

The conductivity of ordinary galvanized iron wire, 
compared with pure copper 100, averages about 14, or 
about one seventh that of pure copper. 

The resistance per statute mile of a galvanized iron 
wire is about ohms at G0° Falir. 

The resistance of iron wire increases about .35 per 
cent, for each degree, Falir. 

The weight per statute mile of 5280 feet, of any cop 
per wire, is ^ d2 T3 lbs. A mile of No. 16 wire weighs 
in practice from 63 to GG lbs. 

The resistance per statute mile of any pure copper 
wire is ohms at G0° Falir. No. 1G copper wire 

of good quality has a resistance of about 19 ohms. 

The resistance of any pure copper wire l inches in 
length, weighing n grains, — ohms. 

O' O O O 7 11 

The resistance of copper increases as the tempera¬ 
ture rises, .21 per cent, for each degree, Falir. 

The conductivity of any copper wire is obtained by 
multiplying its calculated resistance by 100, and divi¬ 
ding the product by its actual resistance. Pure copper 
is taken as 100. 

179. Conducting Powers of Materials. —According 
to the experiments of Mr. M. Gr. Farmer, made some 
years since, the relative electrical resistance of differ¬ 
ent metals and fluids at ordinary temperatures is as fol¬ 
lows, pure copper being taken as 100 : 


Copper Wire. 1.00 

Silver “ 98 

Gold “ 1.13 

Jrori “ 6.03 

Lead “ . 10.'JO 

Mercury “ 60.00 

Palladium Wire. 6.60 

Platinum ** . 6.78 


Tin wire. 6.80 

Zinc “ . 3.70 

Brass “ . 3.88 

German Silver Wire.. 11.30 

Nickel “ 7.70 

Cadmium “ 2.61 

Aluminum “ . 1.71 
























148 


APPENDIX AND NOTES. 


His experiments with fluids gave the following 
results : 


Pure Rain Water. 40,653,723,00 

Water, 12 parts; Sulphuric Acid, 1 part. 1,305,467,00 

Sulphate Copper, 1 pound per gallon . 18,450,000,00 

Saturated solution of common salt. 3,173,000,00 

“ “ of sulphate of zinc. 17,330,000,00 

Nitric Acid, 30 B. 1,606,000,00 


The following table gives the specific resistance in 
ohms of various metals and alloys, at 32° Fahr., 
according to the most recent determinations of Dr. 
Matthiessen : 


t 

Name of Metals. 

Resistance 
of wire 1 
foot long, 
weighing 

1 grain. 

Resistance 
of wire 1 
foot long, 

1- 1000th 
inch in 
diameter. 

Approximate 
per cent, 
variation in 
resistance 
per degree 
temperature 
at 20 degrees. 

Silver annealod. 

0.2214 

9.936 

0.377 

“ hard drawn. 

0.2421 

9.151 


Copper annealed. 

0.2064 

9.718 

0.388 

“ hard drawn. 

0 2106 

9.940 


Gold annealed. 

0.5849 

12 52 

0.365 

“ hard drawn. 

0.5950 

12.74 


Aluminum annealed. 

0.06822 

17.72 


Zinc pressed.. 

0.5710 

32.22 

0.365 

Platinum annealed . 

3 536 

55 09 


Iron annealed . 

1.2425 

59.10 


Nickel annealed . 

1.0785 

75.78 


Tin pressed... 

1.317 

80.36 

0.365 

Lead pressed . 

3.236 

119.39 

0.387 

Mercury liquid. . 

18.746 

600.00 

0.072 

Platinum silver alloy, hard or annealed, used 
for standard resistance coils . 

4.243 

148.35 

0.031 

German silver, hard or annealed, commonly 
used for resistance coils . 

2.652 

127.32 

0.044 

Gold silver alloy, 2 parts gold, 1 part silver, 
hard or annealed . 

2.391 

66.10 

0.065 


The use of this table is as follows : Suppose it is 
required to find the resistance at 32° Fahr. of a con¬ 
ductor of pure hard copper, weighing 400 lbs. per knot. 
This is equivalent to 460 grains per foot. The resist¬ 
ance of a wire weighing one grain is found by the table 
to be 0.2106, therefore the resistance of a foot of wire 
weighing 460 grains will be ^- 6 , but the resistance of 





































MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


149 


one knot will be 6087 times that of one foot, therefore 
the resistance required will be - 6 -- 9J V G ° 0 21 - = 2.79 ohms. 
It the diameter of the wire be given instead of its 
weight per knot, the constant is taken from the second 
column. Thus the resistance at 32° Fahr. of a knot of 
pure hard drawn copper wire 0.1 inch in diameter 
would be *°/ 0 V ro~ = 6.05. The resistance of wires is 
materially altered by annealing them, and a rise in 
temperature increases the resistance of all metals. Dr. 
Matthiessen found that for all pure metals the increase 
of resistance between 32° and 212° Fahr. is sensibly 
the same. The resistance of alloys is much greater 
than the mean of the metals composing them. They 
are very useful in the construction of resistance coils. 

The highest value which has probably been found 
for the conducting power of pure copper is sixty times 
that of pure mercury, according to Sabine. Commer¬ 
cial copper may be considered of good quality when 
its conducting power is over fifty. Different samples 
of copper vary greatly in their specific conductivity, 
as may be seen by the following table, which gives the 
result of careful determinations by Dr. Matthiessen, 
the conducting power of pure copper at 59.9° Fahr. 
being taken as 100. 


Lake Superior, native, not fused .98.8 at 59.9° 

“ “ fused (commercial).... ..92.6 at 59 0° 

Burra Burra.88.7 at 57.2* 

Best selected.81.3 at 57.5° 

Bright copper wire. 72.2 at 60.2° 

Tough copper. 71.0 at 63.1° 

Demidoff. 59.3 at 54.8° 

Rio Tinto. 14.2 at 58.6° 


Thus Rio Tinto copper possesses no better conduct¬ 
ing power than iron. This shows the great importance 
of testing the conductivity of the wire used in the 
manufacture of electro-magnets, cables, etc. 

180. Internal Resistance of Batteries. —This may 
be measured by the sine or tangent galvanometer. 
Place the battery to be measured in circuit with a sine 
galvanometer giving a certain deflection. Insert resist¬ 
ance till the sine of the deflection becomes half what 













150 


APPENDIX AND NOTES. 


it originally was. The total resistance of the circuit 
is now doubled, and the resistance added is, therefore, 
equal to the original resistance. Deduct the resistance 
of the galvanometer and connections from the resist¬ 
ance added, and the remainder is the resistance of the 
battery. 

Second Method .*—Let D = the deflection obtained 
with the battery in circuit with a galvanometer whose 
deflections are proportional, and some resistance r; 
and d the deflection with some larger resistance R (the 
resistance of the galvanometer being included in R and 
r), and let x = the resistance of the battery. 

Then D: d :: R 4 . x : r -f x 


In using this method any other resistance y may be 
included with x , and the formulm becomes— 


x+ y = 


{d Y K) — (D X r) 
1 ) — d, 


and by deducting x we get the value of ?/, or if y be 
large in comparison with x, the flatter may be neglected. 
By this method one resistance r may be compared with 
another. 

The approximate resistance of the batteries in com¬ 
mon use is as follows, according to Mr. Farmer : 


Orovo. 0.41 ohms 

Carbon. 0.0 J “ 

Daniell. 1.70 “ 


181. Electro-motive Force of Different Bat¬ 
teries. —The following table gives approximately the 
electro-motive force of various batteries, beiim the 
mean of numerous observations taken on a sine galvan¬ 
ometer by Mr. Latimer Clark.f The electro-motive 
force of batteries is within certain limits very variable, 
depending on a variety of undetermined causes. It is 
not much affected by temperature. 


* Clark, Electrical Measurement, p. 100. \ Electrical Measurement, p. 108. 










MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 151 

Gr ve’s..... . 100 

Carbon with bi-chromate solution. 107 

Daniell’s. 5G 

Smee’s (when not in action)... 57 

‘‘ (when in action) about. 25 

Copper and zinc in acid (Wollaston). 4G 

Sulphate mercury and graphite (Marie Davy). 7G 

Chloride silver. G2 

Chloride lead. 30 


When connected on short circuit, the electro-motive 
force of several of the batteries, especially Smee’s and 
Wollaston's, will fall off 50 per cent, or more, owing to 
the formation of hydrogen on the negative plate. 
Grove's and Daniell's do not so fall off, because the 
hyd rogen is reduced by the nitric acid in one case and 
by the oxygen in the other. 

182. Measurement of Electro-motive Force.*— 
When a number of cells are joined up in circuit with, 
but in opposition to, a number of other cells with a 
galvanometer inserted, by adjusting the number of 
cells so that no current passes, the relative electro¬ 
motive force of the two batteries may be determined. 

Second Method .—Call the electro-motive forces of the 
two batteries E and E'; join them up successively in 
circuit with the same galvanometer, and by varying 
the resistance, cause them both to give the same de¬ 
flection ; their forces will then be in direct proportion 
to the toted resistances in circuit in each case, or 

R' 

E '- EX I 

where R represents the resistance with E (including 
that of battery, galvanometer, and the adjustable re¬ 
sistance) and R’ with E'. 

183. Forces op Electro-magnets. —The laws which 
govern the forces of electro-magnets have been investi¬ 
gated by Lenz, Jacobi and Muller. 

Let M = the magnetic force of the electro-magnet. 
ii — the number of convolutions ol wire. 
d — the diameter of the solt iron core. 

Q = the quantity of electricity in circulation, 
and c a constant multiplier. 

Then M — c n Q V d. 


* Clark, Electrical Measurement, p. 103. 

















152 


APPENDIX AND NOTES. 


This law only holds good for bars of iron whose 
length is considerably greater than their diameter, for 
feeble currents of electricity, and under the supposi¬ 
tion that the number of convolutions of wire is not so 
great as materially to diminish the influence exerted 
by the outer coils upon the bar of iron. These condi¬ 
tions are fulfilled in the electro-magnets used for tele¬ 
graphic purposes. 

It will be noticed, in the above formulas, that M in¬ 
creases directly as Q and as n, but Q decreases as n 
increases, supposing the electric force to remain con¬ 
stant. Hence it is evident that a certain proportion 
between the resistance of the wire and that of the 
remaining portions of the circuit must be preserved to 
obtain the maximum magnetic force. This relation is 
found to be the following: 

When the resistance of the coils of the electro-magnet 
is equal to the resistance of the rest of the circuit , i. e ., the 
conducting wire and battery, the magnetic force is a maxi¬ 
mum* 

The application of this law to a telegraphic circuit 
would be to make the sum of the resistances of all 
the magnet coils in circuit equal to the resistance of 
the line and batteries, but as in practice the resistance 
of a telegraphic circuit varies, being considerably re¬ 
duced by defective insulation, the total resistance of 
the instruments should be less than that of the line 
when in good condition, to attain the best results dur¬ 
ing unfavorable weather. 

ELECTRICAL FORMULAE. 

184. Ohm’s Law. —Let C = the quantity, or strength, 
or force, or intensity of the current, as it is variously 
called. • 

Let n — the number of cells. 

“ E - the electro-motive force in each cell. 

“ R =. the internal resistance of each cell. 

“ r — the resistances exterior to the battery. 

Then ^ _ n E 

n ii 4- r . 


* Noad’s Students’ Text-book of Electricity, p. 277. • 







MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


153 


185. Parallel or Derived Circuits. —1. The joint 
resistance of any two parallel or derived circuits, whose 
resistances = a and b , is equal to their product divided 
by their sum, or 

R - JLL 
a -f b 

2. The joint resistance of any three circuits, a, b 
and c, is 

a b c 


R = 


ab-\-bc-\-ac 


3. The joint resistance of any number of circuits is 
obtained by adding their reciprocals together, thus: 


r = 


a b c 


186. Galvanometers and Shunts. —1. The joint 
resistance of a galvanometer and shunt is as follows: 


Let g = resistance of galvanometer. 
6 = resistance of shunt. 


Then R = 


<7 5 
9 + 5 


2. The multiplying power of any shunt is equal to 


, or 1 + 1 
s s 


3. To prepare a shunt having some definite multiply¬ 
ing power, for example 10 100 or 1,000, 


Let n = the multiplying power required, 

9 


Then s = 


n — 1 


187. Formula for the Loop Test (127 .—Let x = 
resistance of shortest part of the loop. 

y = resistance of longest part. 

L = total resistance of both. 

R = resistance added to shortest part, to make it equal to the longer. 


Then 


X 4- V = U 









154 


APPENDIX AND NOTES. 


188. Blavier’s Formula for Locating a Fault 
(128).—Let R = resistance of line when in good 
order, S = resistance of defective line when distant 
end is to ground, and T the resistance when it is dis¬ 
connected or open at distant end. 

The distance (a?) of the fault from the testing station 
will be 

x = S — ^ + T R — T S — R 8, 
or x = S — v/ (tt — S) x ('^ S), 

and the resistance of the fault (z) will bo 

z ^ T — S + T R — T~S — it "S 

or z = T — S + ^(R - S) x (T — B) 

180. Measures of Resistance.— 1.045G Siemen’s 
units = 1 ohm. To convert Siemen’s units into ohms, 
multiply by .95G4. 

1 Varlcy’s unit =. 25 ohms. ' , 

1 Megohm = 1,000,0.0 ohms. 

1 Microhm = I ,n r o.oTTo ohras - 

/ Strain of Suspended Wires-.* —The ordinary dip 
of line wires, for a span of 80 yards, is about 18 inches 
in mild weather ; this gives with No. 8 wire a strain 
of 420 lbs., its breaking weight being about 1,300 lbs.— 
(Cutlery.) 

, ... The strain varies directly as the weight of the wire,” 
and inversely as the dip or versine ; it increases as 
the square of the span if the dip be constant; but to 
preserve a given strain the dip or.versine must in¬ 
crease as the square of the span, or, 

X •/ 

L 2 : P ; ; V i v .) 

/ The strain is greater at the point of suspension than’ 
at the lowest point of the span, by a quantity (equal 
to the weight of a length of wire of the same height as 
the versine) which maybe neglected in practice. Call¬ 
ing l the length of the span in feet, w the weight in 


* Clark. Resistance Measurement p. 154. 










MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 


cwts. of one statute mile, v the versine in inches, and 
$ the strain in lbs., 

P X w 

Strain = 3 ] 43 x v ^ s ' a PP rox i ma t e b* 

P X w 

and dip = - . ... . — inches. 

r 31.43 X s 

When both supports are of the same height the 
lowest point in the curve will be in the centre of 
the span ; but if one support be higher than the 
other the lowest point will be near the lower support, 
so that the greater portion of the weight is borne by 
the higher pole. In calculating the strain the wire 
should be considered as if prolonged beyond the lower 
end to a point equal in height to the upper one, and 
the strain will be proportional to the length thus in¬ 
creased, or to twice the distance from the top to the 
bottom of the dip. 

The weight of a wire increases with its strength, the 
quality being the same. The advantage of using thin 
wire for long spans is only in diminishing the weight 
upon the supports. 

Iron expands -nnryir of its length, or about 4io inches 
per mile for every ten degrees of heat.— [C'alley.) 


THE END. 






INDEX. 


Alphabet —Morse, 101 ; Formation of the, 96 ; Exercises for practising, 97; 

Spaced letters in, 101. 

American Compound Wire, the, 89-104. 

Apparatus, adjustment of the, 36. 

Appendix and Notes, 116. 

Armature, 22. 

Atlantic Cables, method of working, 141. 

Batteries— Insulation of, 20 ; Paraffined jars for, 20 ; Arrangement of, 26 ; 
Reversed, 57 ; Table of Resistances of, 117; Table of electro-motive 
forces of, 117; Measurement of electro-motive forces of, 151; Working 
several lines from, 71; Electrical tension of, 124. 

Battery, Carbon, or Electropoion, 17; Setting up the, 18; Solution, recipe 
for making, 19 ; Renewal of the, 19 ; Resistance of, 117, 151 ; Electro¬ 
motive force of, 117, 151. 

Battery, Daniell— 12; Effect of continued action on the, 13; Deposit of cop¬ 
per upon porous cup of the, 14; Renewal of the, 14 ; Application to 
main circuit of the, 15. 

Battery, Grove— 15; Setting up a, 16 ; Renewal of the, 17; Resistance of, 
117, 150; Electro-motive force of, 117, 151. 

Battery, Gravity— 106; Callaud, 106; Hill, 106 ; Manner of setting up, 107 ; 
Maintenance of, 107 ; Internal resistance of, 117, 149 ; Electro-motive 
force of, 117. 

Battery Power— Distribution of, 70. 

Binding Screws, 57. 

Bridge, Wheatstone’s, 109, 110. 

Button Repeater —Wood’s, 46, Edison’s, 134. 


Cables, 93; Making joints in, 94. 

Cables, Atlantic—Mode of working the, 141. 

Circuit, 57; Simple galvanic, 9; Earth, 26; Metallic, 57; Local, 30, 57. 
Circuits, Telegraphic, 24, 25. 

Circuit Changer, for locals, 56. 

Compound Wire, the American, 89,104. 

Combination Printing Instrument, the, 27. 

Combination, locals, 55. 

Condenser, used in working Atlantic Cable, 141. 

Conductivity resistance, testing for, 87. 

Conductors and Non-conductors, 5; Table of, 5. 



158 


INDEX. 


Conducting power of Materials* Table of, 147. 

Construction, telegraphic, notes on, 89. 

Cross, 57, 73 ; Weather do., 57, 73 ; Testing for, 76; To find the distance of, 
85. 

Cross Connecting Wires, 57, 75. 

Current, Effective force of, 24; Laws of, 64. 

Currents, Earth, 88, 141. 

Derived Circuits, formula for, 153. 

Disconnection, 73; Testing for, 75; Partial do., 73; Testing for 75. 

Diameters of Wires, table of, 146. 

Double Transmission, 131. 

Earth Circuit, the, 23; Resistance of, 26. 

Earth Currents, 88, 141. 

Electric Currents, laws of the, 64. 

Electric Signals, velocity of, 144. 

Electro-magnets, forces of, 151. 

Electro-magnet, 21, 22; Cores of, 21; Construction of, 22. 
Electro-magnetism, 21. 

Electro-motive Forces, measurement of, 151; Table of, 117, 151. 

Escape, 57, 63, 73 ; Testing for, 75 ; Blavier’s formula for locating, 84, 154; 

Effects of upon the circuit, 63. 

Equipment of Telegraph Lines, the, 117. 

Faults, Testing for distance of, 80. 

Formula —Blavier’s, for locating an escapb, 84, 154 ; For weight and resist¬ 
ance of wires, 147 ; Electrical, 152; Ohm’s, 152 ; Parallel or derived cir¬ 
cuits, 153; Joint resistance of parallel circuits, 153; Galvanometers and 
shunts, 153; For the loop test, 153. 

Galvanometer, 21 ; Testing with, 78 ; Differential, 78,109 ; Siemens Univer¬ 
sal, 108, 111; Bradley’s tangent, 135; Thompson’s reflecting, 137. 
Galvanometers and Shunts, formula for resistance of, 153. 

Gauges, wire, comparison of, 146. 

Grounds, testing for, 76. 

Ground Connections, 93; Defective, testing for, 74 
Ground Switch, 36, 38. 

• 

Insulation, 58 ; English standard of, 86 ; Mileage, 86. 

Insulator —Glass, 59 ; Wade, 60 ; Hard rubber, 60 ; Lefferts’, 61 ; Brooks*. 
61, 62. 

Insulators, mode of testing, 62; Fixing upon poles, 91. 

Interruptions upon Lines, 73. 

Internal Resistance of Batteries, 149. 

Joints or Splices, 90; In Cables, method of making, 94 
Joint Resistance, 67, 121; Formula for, 126. 


INDEX. 


159 


Lightning Arresters, 42; Chester’s plate, 43; Bradley’s, 43. 

Locals, 57; Combination, 55. 

Local Circuit Changer, 5G. 

Line, 57. 

Loop, 57. 

Loop test, the, 81; Formula for, ib3. 

Leading Wires into Offices, 92. 

Learners. Hints to, 97. 

Magnets, Electro, 20; Formula for forces of, 151. 

Measures, Electrical, 154. 

Measurement, Electrioal, 25; Standards of, 25,154; Advantages of testing by, 
80. 

Morse System, the, 26, 28; Signal key of the, 28; Register of the, 29; Relay 
magnet of the, 30; Alphabet of the, 101. 

Notes on Telegraphic Construction, 89. 

Notes, Appendix and, 116. 

Ohm, definition of the, 25. 

Ohm's Law, 64, 152; Practical application of, 64. 

Offices, leading wires into, 92; Fitting up, 92; Arrangement of wires in, 34, 
35. 

Poles, Telegraph, 89. 

Printing Telegraph— the combination, 27; Pope and Edison’s, 112. 
Quantity, Electrical, 11. 

Resistance, 10; Of the circuit, 42 ; Units of, 25, 154 ; Conductivity, testing 
for, 87 ; Of unsoldered joints, 87 ; of relays, 117; Of Batteries, table of 
117; Of different metals, table of, 148; Of liquids, 148; Of copper, 149; 
Of batteries, to ascertain the, 149. 

Resistance Coils, 25; Testing with, 78. 

Register, Morse, the, 29; Mainline, the, 34; Proper resistance of, 118. 

Relay, the Morse, 30; Pocket, the, 32. 

Relays —Proper resistance for, 117. 

Reading by Sound, 102. 

Repeaters, 45 ; Wood’s button, 46 ; Hicks’ automatic, 47 ; Milliken’s, 50; 

Bunnell’s, 52; Edison’s button, 107. 

Recent Improvements in Telegraph Practice, 104. 

Service, Telegraphic —Technical terms used in the, 57. 

Siemens’ unit, 151; Universal galvanometer, 108, 111. 

Shunts— of galvanometer, 80 ; Formula for resistance of, 153 ; Multiplying 
power of, 80, 153. 

Signal Key, the Morse, 28. 

Signals Electric, velocity of, 141. 

Sounder, the Morse, 32; Main line, the, 33; Proper resistance of, 118. 



160 


INDEX. 


Sound, reading by, 102. 

Splices or Joints, 90. 

Speed of Transmission, 145. 

Stations, intermediate, 26 ; Arrangement of, 35 ; Terminal, arrangement of, 
34. 

Strain of Suspended Wires, 151. 

Switch —Ground, 36, 38 ; Button, 37; Plug, 39 ; Universal, 40 ; Culgan, 40 ; 
Jones’ lock, 41. 

Switches or Commutators, 37. 

Technical Terms Used in the Telegraph Service, 57. 

Tension, electrical, 11; Of batteries and lines, 124; Diagram of, 128. 

Telegraph Lines— Equipment of, 116 ; Electrical tension of, 124 ; Working 
capacity of, 121. 

Telegraphic Construction, notes on, 89. 

Test, the loop, 81. 

Testing —Insulators, 62; Telegraph lines, 73 ; For disconnection, 74; Partial 
disconnection, 75 ; Escape, 75 ; Cross, 76 ; Ground, 76 ; By galvano¬ 
meter and resistance coils, 78 ; For distance of faults, 80 ; By measure¬ 
ment, advantages of, 86; For conductivity resistance, 87. 

Transmission— Double, 131 ; Speed of, 145. 

Units of Electrical Measurement —British Association or Ohm, 25, 154 ; 
Siemens’, 154; Varley’s, 154. 

Velocity of Electric Signals, 144. 

Varley’s Unit of Measurement, 154. 

Weather Cross, 57. 

Wires— To cross connect, 57, 75 ; To put straight, 57 ; To ground, 57 ; To 
open, 57 ; Arrangement of, upon the poles, 90 ; Method of splicing, 90 ; 
Strain of, when suspended, 154. 

Wire— For telegraph lines, 89 ; American compound, 89, 104; Galvanized, 
90 ; Table of diameters of, 119; Iron, formula for ascertaining weight 
of, 147 ; Resistance of, 147 ; Copper, weight of, 147; Resistance of, 
147. 

Wire Gauges, comparison of, 146. 

Wheatstone’s Bridge, 109, 110. 

Working Capacity of Telegraph Lines, 121 ; How to increase, 121. 


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with an introduction to the Calculus, by Eckley B. Coxe, A. M., 
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Francis’ Lowell Hydraulics. 

Third Edition. 4to. Cloth. $15.00. 

Lowell Hydraulic Experiments —being a Selection from Experi¬ 
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S Vols. 4to, with Tort folio of Maps. Cloth. $30.00. 

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King’s Notes on Steam. 

Nineteenth Edition. 8vo. $2.00. 

Lessons and Practical Notes on Steam, —the Steam Engine, Propel¬ 
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Ancliincloss. 

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Application of the Slide Valve and Link Motion to Stationary, 
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Stillman’s Steam-Engine Indicator. 

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< 

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Ward’s Steam for tlie Million. 

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Tunner on Roll-Turning. 

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A Treatise on Roll-Turning for the Manufacture of Iron, 
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• • 

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Barba on tlie Use of Steel. 

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Bell on Iron Smelting. 

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Collins’ Useful Alloys. 

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Joynson’s Metal Used in Construction. 

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Treatise on Ore Deposits. By Bernhard Yon Cotta, Professor 
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Plattner’s Blow-Pipe Analysis. 

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Pynchon’s Chemical Physics. 

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Prescott’s Proximate Organic Analysis. 

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Prescott’s Alcoliolic Liquors. 

12mo. Cloth. $1.50. 

Chemical Examination of Alcoholic Liquors. —A Manual of the 
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Albert B. Prescott, Professor of Organic and Applied Chemistry 
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Prescott and Douglas’s Qualitative Chemi- 

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A Guide in the Practical Study of Chemistry and in the Work of Analysis. 

Pope’s Modern Practice of the Electric 

Telegraph. 

Ninth Edition. 8vo. Cloth. $2.00. 

A Hand-book for Electricians and Operators. By Frank L. Poi»e. 
Ninth edition. Itevised and enlarged, and fully illustrated. 

Sabine’s History of the Telegraph. 

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History and Progress of the Electric Telegraph, with De¬ 
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Haskins’ Galvanometer. 

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Larrabee’s Secret Letter and Telegraph 

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C ipher and Secret Letter and Telegraphic Code, with Hogg s 

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. 











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Gillmore’s Limes and Cements. 

Fifth Edition. Revised and Enlarged. 8vo. Cloth. $4.00. 

Practical Treatise on Limes, Hydraulic Cements, and Mor¬ 
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Gfllmore’s Coignet Beton. 

Nine Plates, Views, etc. 8vo. Cloth. $2.50. 

Coignet Beton and Other Artificial Stone. —By Q. A. Gill- 
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Grillmore on Hoads. 

Seventy Illustrations. 12mo. Cloth. $2.00. 

A Practical Treatise on the Construction of Roads, Streets, 
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Gillmore’s Building Stones. 

8 vo. Cloth. $1;50. 

Report on Strength of the Building Stones in the United 
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Holley’s Railway Practice. 

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American and European Railway Practice, in the Economical 
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and the adaptation of Wood and Coke-burning Engines to Coal¬ 
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Useful Information, for Railway Men. 

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Compiled by W. G. Hamilton, Engineer. Sixth Edition, Revised 
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D. VAN NOSTRAND. 11 


Stuart’s Civil and. Military Engineering of 

America. 

8vo. Illustrated. Clotli. $5.00. 

The Civil and Military Engineers of America. By General 
Charles B. Stuart, Author of “ Naval Dry Docks of the United 
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Ernst’s Manual of Military Engineering. 

193 Wood-cuts and 3 Lithographed Plates. 12mo. Cloth. $5.00. 

A Manual of Practical Military Engineering. Prepared for 
the use of the Cadets of the U. S. Military Academy, and for Engineer 
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Simms’ Levelling. 

12mo. Cloth. $2.50. 

A Treatise on the Principles and Practice of Levelling, 
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Mr. Law’s Practical Examples for Setting-out Railway Curves. 
Illustrated with three lithographic plates and numerous wood-cuts. 

Jeffers’ Nautical Surveying. 

Illustrated with 9 Copperplates and 31 Wood-cut Illustrations. 8vo. Cloth. $5.00. 

Nautical Surveying. By William N. Jeffers, Captain U. S. 
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Text-book of Surveying. 

8vo. 9 Lithograph Plates and several Wood-cuts. Cloth. $2.00. 

A Text-book on Surveying, Projections, and Portable Instruments, 
for the use of the Cadet Midshipmen, at the U. S. Naval Academy. 

Th.e Plane Table. 

8vo. Cloth. $2.00. 

Its Uses in Topographical Surveying. From the papers of the 
U. S. Coast Survey. 










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Cliauvenet’s Lunar Distances. 

8vo. Clotli. $2.00. 

New Method of Correcting Lunar Distances, and Improved 
Method of Findin-g the Error and Rate of a Chronometer, by equal 
altitudes. By Wm. Ciiauvenet, LL.D., Chancellor of Washington 
University of St. Louis. 

Burt’s Key to Solar Compass. 

Second Edition. Pocket-book form. Tuck. $2.50. 

Ivey to the Solar Compass, and Surveyor’s Companion ; comprising 
all the Rules necessary for use in the Field ; also Description of the 
Linear Surveys and Public Land System of the United States, Notes 
on the Barometer, Suggestions for an Outfit for a Survey of Four 
Months, etc. By W. A. Burt, U. S. Deputy Surveyor. 

Howard’s Earthwork Mensuration. 

8vo. Illustrated. Cloth. $1.50. 

Earthwork Mensuration on the Basis of the Prismoidal 
FoRMULiE. Containing simple and labor-saving method of obtaining 
Prismoidal Contents directly from End Areas. Illustrated by 
Examples, and accompanied by Plain Rules for practical uses. By 
Conway R. Howard, Civil Engineer, Richmond, Ya. 

Morris’ Easy Rules. 

78 Illustrations. 8vo. Cloth. $1.50. 

Easy Rules for the Measurement of Earthworks, by means of 
the Prismoidal Formula. By Elwood Morris, Civil Engineer. 

Clevenger’s Surveying. 

Illustrated Pocket Form. Morocco, gilt. $2.50. 

A Treatise on the Method of Government Surveying, as 
prescribed by the U. S. Congress and Commissioner of the General 
Land Office. With complete Mathematical, Astronomical, and Prac¬ 
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Students who contemplate engaging in the business of Public Land 
Surveying. By S. V. Clevenger, U. S. Deputy Surveyor. 

Hewson on Embankments. 

8vo. Cloth. $2.00. 

Principles and Practice of Embanking Lands from River 
Floods, as applied to the Levees of the Mississippi. By William 
Hewson, Civil Engineer. 















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13 


t \ . 

Minifie’s Mechanical Drawing. 

Ninth Edition. Royal 8vo. Cloth. $4.00. 

A Text-Book of Geometrical Drawing, for the use of Mechanics 
and Schools. With illustrations for Drawing Plans, Sections, and 
Elevations of Buildings and Machinery ; an Introduction to Isometri- 
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With over 200 diagrams on steel. By William Minifie, Architect. 
With an Appendix on the Theory and Application of Colors. 

Minifie’s Geometrical Drawing. 

New Edition. Enlarged. 12mo. Cloth. $2.00. 

Geometrical Drawing. Abridged from the octavo edition, for the 
use of Schools. Illustrated with 48 steel plates. 

Free Hand. Drawing. 

Profusely Illustrated. 18ino. Boards. 50 cents. 

A Guide to Ornamental, Figure, and Landscape Drawing. By an 
Art Student. 


The Mechanic’s Friend. 

12mo. Cloth. 300 Illustrations. $1.50. 

The Mechanic’s Friend. A Collection of Receipts and Practical 
Suggestions, relating to Aquaria—Bronzing—Cements—Drawing— 
Dyes—Electricity—Gilding—Glass-working—Glues—Horology— Lac¬ 
quers—Locomotives—Magnetism—Metal-working— Modelling— Pho¬ 
tography—Pyrotechny—Railways — Solders — Steam-Engine — Tele¬ 
graphy—Taxidermy—Varnishes—Waterproofing—and Miscellaneous 
Tools, Instruments, Machines, and Processes connected with the 
Chemical and Mechanical Arts. By William E. Axon, M.R.S.L. 

Harrison’s Mechanic’s Tool-Book. 

44 Illustrations. 12mo. Cloth. $1.50. 

Mechanics’ Tool Book, with Practical Rules and Suggestions, for the 
use of Machinists, Iron Workers, and others. By W. B. Harrison. 

Bandall’s Qnartz Operator’s Hand-Book. 

12mo. Cloth. $2 00. 

Quartz Operator’s Hand-Book. By P. M. Randall. New 
edition, Revised and Enlarged. Fully illustrated. 

















14 SCIENTIFIC BOOKS PUBLISHED BY 


Joynson on Machine Gearing. 

8 vo. Cloth. $2.00. 

Tiie Mechanic’s and Student’s Guide in the designing and Con* 
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Wheels, etc., and the Drawing of Rectilineal and Curved Surfaces. 
Edited by Francis II. Joynson. With 18 folded plates. 

Silversmith’s Hand-Book. 

Fourth Edition. Illustrated. 12mo. Cloth. $3.00. 

A Practical Hand-Book for Miners, Metallurgists, and Assayers. 
By Julius Silversmith. Illustrated. 

Barnes’ Submarine Warfare. 

8vo. Cloth. $5.00. 

Submarine Warfare, Defensive and Offensive. Descriptions 
of the various forms of Torpedoes, Submarine Batteries and Torpedo 
Boats actually used in War. Methods of Ignition by Machinery, 
Contact Fuzes, and Electricity, and a full account of experiments 
made to determine the Explosive Force of Gunpowder under Water. 
Also a discussion of the Offensive Torpedo system, its effect upon 
Iron-clad Ship systems, and influence upon future Naval Wars. By 
Lieut.-Com. John S. Barnes, U.S.N. With twenty lithographic 
plates and many wood-cuts. 

Foster’s Submarine Blasting. 

4to. Cloth. $3.50. 

Submarine Blasting, in Boston Harbor, Massachusetts—Removal of 
Tower and Corwin Rocks. By John G. Foster, U. S. Eng. and 
Bvt. Major-General U. S. Army. With seven plates. 

Mowbray’s Tri-Nitro-Glycerine. 

8vo. Cloth. Illustrated. $3.00. 

Tri-Nitro-Glycerine, as applied in the Hoosac Tunnel, and to Sub¬ 
marine Blasting, Torpedoes, Quarrying, etc. 

Williamson on the Barometer. 

4 to. Cloth. $15.00. 

On the Use of the Barometer on Surveys and Reconnais¬ 
sances. Part I.—Meteorology in its Connection with Hypsometry. 
Part II.—Barometric Hypsometry. By R. S. Williamson, Bvt. 
Lt.-Col. U. S. A., Major Corps of Engineers. With illustrative tables 
and engravings. 









D. VAN NOSTRAND. 


15 


Williamson’s Meteorological Tables. 

4to. Flexible Cloth. $2.50. 

Practical Tables in Meteorology and Hypsometry, in connection 
with the use of the Barometer. By Col. R. S. Williamson, U.S.A. 

Butler’s Projectiles and Rifled Cannon. 

4to. 3G Plates. Cloth. $7.50. 

Projectiles and Rifled Cannon. A Critical Discussion of the 
Principal Systems of Rifling and Projectiles, with Practical Sugges¬ 
tions for their Improvement. By Capt. John S. Butler, Ordnance 
Corps, U. S. A. 

Benet’s Chronoscope. 

Second Edition. Illustrated. 4to. Cloth. $3.00. 

Electro-Ballistic Machines, and the Schultz Chronoscope. By 
Lt.-Col. S. Y. Benet, Chief of Ordnance U. S. A. 

Michaelis’ Chronograph. 

4to. Illustrated. Cloth. $3.00. 

The Le Boulenge Chronograph. With three lithographed folding 
plates of illustrations. By Bvt. Captain O. E. Michaelis, Ordnance 
Corps, U. S. A. 

Nugent on Optics. 

12mo. Cloth. $1.50. 

Treatise on Optics ; or, Light and Sight, theoretically and practically 
treated; with the application to Fine Art and Industrial Pursuits. 
By E. Nugent. With 103 illustrations. 

Peirce’s Analytic Mechanics. 

4to. Cloth. $10.00. 

System of Analytic Mechanics. By Benjamin Peirce, Pro¬ 
fessor of Astronomy and Mathematics in Harvard University. 

Craig’s Decimal System. 

Square 32mo. Limp. 50<x 

Weights and Measures. An Account of the Decimal System, with 
Tables of Conversion for Commercial and Scientific Uses. By B. F. 
Craig, M.D. 




















16 SCIENTIFIC BOOKS PUBLISHED BY 


Alexander’s Dictionary of Weights and 

Measures. 

New Edition. 8vo. Cloth. $3.50. 

Universal Dictionary of Weights and Measures, Ancient and 
Modern, reduced to the standards of the United States of America. 
By J. H. Alexander. 

Elliot’s European Light-Douses. 

51 Engravings and 21 Wood-cuts. 8vo. Cloth. $5.00. 

European Ligiit-House Systems. Being a Report of a Tour of 
L Inspection made in 1873. By Major George H. Elliot, U. S. 
Engineers. 

Sweet’s Report on Coal. 

With Maps. 8vo. Cloth. $3.00. 

Special Report on Coal. By S. H. Sweet. 

Colburn’s Gas Works of London. 

12mo. Boards. 60 cents. 

Gas Works of London. By Zerah Colburn. 

Walker’s Screw Propulsion. 

8vo. Cloth. 75. cents. 

Notes on Screw Propulsion, its Rise and History. By Capfc. W. H. 
Walker, U. S. Navy. 

Pook on Shipbuilding. 

8vo. Cloth. Illustrated. $5.00. 

Method of Preparing the Lines and Draughting Vessels 
Propelled by Sail or Steam, including a Chapter on Laying-off 
on the Mould-loft Floor. By Samuel M. Pook, Naval Constructor. 

Saeltzer’s Acoustics. 

12mo. Cloth. $2.00. 

Treatise on Acoustics in connection with Ventilation. By Alex¬ 
ander Saeltzer. 

Eassie on Wood and its TIses. 

250 Illustrations. 8vo. Cloth. $1.50. 

A Hand-book for the Use of Contractors, Builders, Architects, 
Engineers, Timber Merchants, etc., with information for drawing up 
Designs and Estimates. 




















































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